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Based on kernel version 3.15.4. Page generated on 2014-07-07 09:03 EST.

2			Linux Ethernet Bonding Driver HOWTO
4			Latest update: 27 April 2011
6	Initial release : Thomas Davis <tadavis at lbl.gov>
7	Corrections, HA extensions : 2000/10/03-15 :
8	  - Willy Tarreau <willy at meta-x.org>
9	  - Constantine Gavrilov <const-g at xpert.com>
10	  - Chad N. Tindel <ctindel at ieee dot org>
11	  - Janice Girouard <girouard at us dot ibm dot com>
12	  - Jay Vosburgh <fubar at us dot ibm dot com>
14	Reorganized and updated Feb 2005 by Jay Vosburgh
15	Added Sysfs information: 2006/04/24
16	  - Mitch Williams <mitch.a.williams at intel.com>
18	Introduction
19	============
21		The Linux bonding driver provides a method for aggregating
22	multiple network interfaces into a single logical "bonded" interface.
23	The behavior of the bonded interfaces depends upon the mode; generally
24	speaking, modes provide either hot standby or load balancing services.
25	Additionally, link integrity monitoring may be performed.
27		The bonding driver originally came from Donald Becker's
28	beowulf patches for kernel 2.0. It has changed quite a bit since, and
29	the original tools from extreme-linux and beowulf sites will not work
30	with this version of the driver.
32		For new versions of the driver, updated userspace tools, and
33	who to ask for help, please follow the links at the end of this file.
35	Table of Contents
36	=================
38	1. Bonding Driver Installation
40	2. Bonding Driver Options
42	3. Configuring Bonding Devices
43	3.1	Configuration with Sysconfig Support
44	3.1.1		Using DHCP with Sysconfig
45	3.1.2		Configuring Multiple Bonds with Sysconfig
46	3.2	Configuration with Initscripts Support
47	3.2.1		Using DHCP with Initscripts
48	3.2.2		Configuring Multiple Bonds with Initscripts
49	3.3	Configuring Bonding Manually with Ifenslave
50	3.3.1		Configuring Multiple Bonds Manually
51	3.4	Configuring Bonding Manually via Sysfs
52	3.5	Configuration with Interfaces Support
53	3.6	Overriding Configuration for Special Cases
55	4. Querying Bonding Configuration
56	4.1	Bonding Configuration
57	4.2	Network Configuration
59	5. Switch Configuration
61	6. 802.1q VLAN Support
63	7. Link Monitoring
64	7.1	ARP Monitor Operation
65	7.2	Configuring Multiple ARP Targets
66	7.3	MII Monitor Operation
68	8. Potential Trouble Sources
69	8.1	Adventures in Routing
70	8.2	Ethernet Device Renaming
71	8.3	Painfully Slow Or No Failed Link Detection By Miimon
73	9. SNMP agents
75	10. Promiscuous mode
77	11. Configuring Bonding for High Availability
78	11.1	High Availability in a Single Switch Topology
79	11.2	High Availability in a Multiple Switch Topology
80	11.2.1		HA Bonding Mode Selection for Multiple Switch Topology
81	11.2.2		HA Link Monitoring for Multiple Switch Topology
83	12. Configuring Bonding for Maximum Throughput
84	12.1	Maximum Throughput in a Single Switch Topology
85	12.1.1		MT Bonding Mode Selection for Single Switch Topology
86	12.1.2		MT Link Monitoring for Single Switch Topology
87	12.2	Maximum Throughput in a Multiple Switch Topology
88	12.2.1		MT Bonding Mode Selection for Multiple Switch Topology
89	12.2.2		MT Link Monitoring for Multiple Switch Topology
91	13. Switch Behavior Issues
92	13.1	Link Establishment and Failover Delays
93	13.2	Duplicated Incoming Packets
95	14. Hardware Specific Considerations
96	14.1	IBM BladeCenter
98	15. Frequently Asked Questions
100	16. Resources and Links
103	1. Bonding Driver Installation
104	==============================
106		Most popular distro kernels ship with the bonding driver
107	already available as a module. If your distro does not, or you
108	have need to compile bonding from source (e.g., configuring and
109	installing a mainline kernel from kernel.org), you'll need to perform
110	the following steps:
112	1.1 Configure and build the kernel with bonding
113	-----------------------------------------------
115		The current version of the bonding driver is available in the
116	drivers/net/bonding subdirectory of the most recent kernel source
117	(which is available on http://kernel.org).  Most users "rolling their
118	own" will want to use the most recent kernel from kernel.org.
120		Configure kernel with "make menuconfig" (or "make xconfig" or
121	"make config"), then select "Bonding driver support" in the "Network
122	device support" section.  It is recommended that you configure the
123	driver as module since it is currently the only way to pass parameters
124	to the driver or configure more than one bonding device.
126		Build and install the new kernel and modules.
128	1.2 Bonding Control Utility
129	-------------------------------------
131		 It is recommended to configure bonding via iproute2 (netlink)
132	or sysfs, the old ifenslave control utility is obsolete.
134	2. Bonding Driver Options
135	=========================
137		Options for the bonding driver are supplied as parameters to the
138	bonding module at load time, or are specified via sysfs.
140		Module options may be given as command line arguments to the
141	insmod or modprobe command, but are usually specified in either the
142	/etc/modrobe.d/*.conf configuration files, or in a distro-specific
143	configuration file (some of which are detailed in the next section).
145		Details on bonding support for sysfs is provided in the
146	"Configuring Bonding Manually via Sysfs" section, below.
148		The available bonding driver parameters are listed below. If a
149	parameter is not specified the default value is used.  When initially
150	configuring a bond, it is recommended "tail -f /var/log/messages" be
151	run in a separate window to watch for bonding driver error messages.
153		It is critical that either the miimon or arp_interval and
154	arp_ip_target parameters be specified, otherwise serious network
155	degradation will occur during link failures.  Very few devices do not
156	support at least miimon, so there is really no reason not to use it.
158		Options with textual values will accept either the text name
159	or, for backwards compatibility, the option value.  E.g.,
160	"mode=802.3ad" and "mode=4" set the same mode.
162		The parameters are as follows:
164	active_slave
166		Specifies the new active slave for modes that support it
167		(active-backup, balance-alb and balance-tlb).  Possible values
168		are the name of any currently enslaved interface, or an empty
169		string.  If a name is given, the slave and its link must be up in order
170		to be selected as the new active slave.  If an empty string is
171		specified, the current active slave is cleared, and a new active
172		slave is selected automatically.
174		Note that this is only available through the sysfs interface. No module
175		parameter by this name exists.
177		The normal value of this option is the name of the currently
178		active slave, or the empty string if there is no active slave or
179		the current mode does not use an active slave.
181	ad_select
183		Specifies the 802.3ad aggregation selection logic to use.  The
184		possible values and their effects are:
186		stable or 0
188			The active aggregator is chosen by largest aggregate
189			bandwidth.
191			Reselection of the active aggregator occurs only when all
192			slaves of the active aggregator are down or the active
193			aggregator has no slaves.
195			This is the default value.
197		bandwidth or 1
199			The active aggregator is chosen by largest aggregate
200			bandwidth.  Reselection occurs if:
202			- A slave is added to or removed from the bond
204			- Any slave's link state changes
206			- Any slave's 802.3ad association state changes
208			- The bond's administrative state changes to up
210		count or 2
212			The active aggregator is chosen by the largest number of
213			ports (slaves).  Reselection occurs as described under the
214			"bandwidth" setting, above.
216		The bandwidth and count selection policies permit failover of
217		802.3ad aggregations when partial failure of the active aggregator
218		occurs.  This keeps the aggregator with the highest availability
219		(either in bandwidth or in number of ports) active at all times.
221		This option was added in bonding version 3.4.0.
223	all_slaves_active
225		Specifies that duplicate frames (received on inactive ports) should be
226		dropped (0) or delivered (1).
228		Normally, bonding will drop duplicate frames (received on inactive
229		ports), which is desirable for most users. But there are some times
230		it is nice to allow duplicate frames to be delivered.
232		The default value is 0 (drop duplicate frames received on inactive
233		ports).
235	arp_interval
237		Specifies the ARP link monitoring frequency in milliseconds.
239		The ARP monitor works by periodically checking the slave
240		devices to determine whether they have sent or received
241		traffic recently (the precise criteria depends upon the
242		bonding mode, and the state of the slave).  Regular traffic is
243		generated via ARP probes issued for the addresses specified by
244		the arp_ip_target option.
246		This behavior can be modified by the arp_validate option,
247		below.
249		If ARP monitoring is used in an etherchannel compatible mode
250		(modes 0 and 2), the switch should be configured in a mode
251		that evenly distributes packets across all links. If the
252		switch is configured to distribute the packets in an XOR
253		fashion, all replies from the ARP targets will be received on
254		the same link which could cause the other team members to
255		fail.  ARP monitoring should not be used in conjunction with
256		miimon.  A value of 0 disables ARP monitoring.  The default
257		value is 0.
259	arp_ip_target
261		Specifies the IP addresses to use as ARP monitoring peers when
262		arp_interval is > 0.  These are the targets of the ARP request
263		sent to determine the health of the link to the targets.
264		Specify these values in ddd.ddd.ddd.ddd format.  Multiple IP
265		addresses must be separated by a comma.  At least one IP
266		address must be given for ARP monitoring to function.  The
267		maximum number of targets that can be specified is 16.  The
268		default value is no IP addresses.
270	arp_validate
272		Specifies whether or not ARP probes and replies should be
273		validated in any mode that supports arp monitoring, or whether
274		non-ARP traffic should be filtered (disregarded) for link
275		monitoring purposes.
277		Possible values are:
279		none or 0
281			No validation or filtering is performed.
283		active or 1
285			Validation is performed only for the active slave.
287		backup or 2
289			Validation is performed only for backup slaves.
291		all or 3
293			Validation is performed for all slaves.
295		filter or 4
297			Filtering is applied to all slaves. No validation is
298			performed.
300		filter_active or 5
302			Filtering is applied to all slaves, validation is performed
303			only for the active slave.
305		filter_backup or 6
307			Filtering is applied to all slaves, validation is performed
308			only for backup slaves.
310		Validation:
312		Enabling validation causes the ARP monitor to examine the incoming
313		ARP requests and replies, and only consider a slave to be up if it
314		is receiving the appropriate ARP traffic.
316		For an active slave, the validation checks ARP replies to confirm
317		that they were generated by an arp_ip_target.  Since backup slaves
318		do not typically receive these replies, the validation performed
319		for backup slaves is on the broadcast ARP request sent out via the
320		active slave.  It is possible that some switch or network
321		configurations may result in situations wherein the backup slaves
322		do not receive the ARP requests; in such a situation, validation
323		of backup slaves must be disabled.
325		The validation of ARP requests on backup slaves is mainly helping
326		bonding to decide which slaves are more likely to work in case of
327		the active slave failure, it doesn't really guarantee that the
328		backup slave will work if it's selected as the next active slave.
330		Validation is useful in network configurations in which multiple
331		bonding hosts are concurrently issuing ARPs to one or more targets
332		beyond a common switch.  Should the link between the switch and
333		target fail (but not the switch itself), the probe traffic
334		generated by the multiple bonding instances will fool the standard
335		ARP monitor into considering the links as still up.  Use of
336		validation can resolve this, as the ARP monitor will only consider
337		ARP requests and replies associated with its own instance of
338		bonding.
340		Filtering:
342		Enabling filtering causes the ARP monitor to only use incoming ARP
343		packets for link availability purposes.  Arriving packets that are
344		not ARPs are delivered normally, but do not count when determining
345		if a slave is available.
347		Filtering operates by only considering the reception of ARP
348		packets (any ARP packet, regardless of source or destination) when
349		determining if a slave has received traffic for link availability
350		purposes.
352		Filtering is useful in network configurations in which significant
353		levels of third party broadcast traffic would fool the standard
354		ARP monitor into considering the links as still up.  Use of
355		filtering can resolve this, as only ARP traffic is considered for
356		link availability purposes.
358		This option was added in bonding version 3.1.0.
360	arp_all_targets
362		Specifies the quantity of arp_ip_targets that must be reachable
363		in order for the ARP monitor to consider a slave as being up.
364		This option affects only active-backup mode for slaves with
365		arp_validation enabled.
367		Possible values are:
369		any or 0
371			consider the slave up only when any of the arp_ip_targets
372			is reachable
374		all or 1
376			consider the slave up only when all of the arp_ip_targets
377			are reachable
379	downdelay
381		Specifies the time, in milliseconds, to wait before disabling
382		a slave after a link failure has been detected.  This option
383		is only valid for the miimon link monitor.  The downdelay
384		value should be a multiple of the miimon value; if not, it
385		will be rounded down to the nearest multiple.  The default
386		value is 0.
388	fail_over_mac
390		Specifies whether active-backup mode should set all slaves to
391		the same MAC address at enslavement (the traditional
392		behavior), or, when enabled, perform special handling of the
393		bond's MAC address in accordance with the selected policy.
395		Possible values are:
397		none or 0
399			This setting disables fail_over_mac, and causes
400			bonding to set all slaves of an active-backup bond to
401			the same MAC address at enslavement time.  This is the
402			default.
404		active or 1
406			The "active" fail_over_mac policy indicates that the
407			MAC address of the bond should always be the MAC
408			address of the currently active slave.  The MAC
409			address of the slaves is not changed; instead, the MAC
410			address of the bond changes during a failover.
412			This policy is useful for devices that cannot ever
413			alter their MAC address, or for devices that refuse
414			incoming broadcasts with their own source MAC (which
415			interferes with the ARP monitor).
417			The down side of this policy is that every device on
418			the network must be updated via gratuitous ARP,
419			vs. just updating a switch or set of switches (which
420			often takes place for any traffic, not just ARP
421			traffic, if the switch snoops incoming traffic to
422			update its tables) for the traditional method.  If the
423			gratuitous ARP is lost, communication may be
424			disrupted.
426			When this policy is used in conjunction with the mii
427			monitor, devices which assert link up prior to being
428			able to actually transmit and receive are particularly
429			susceptible to loss of the gratuitous ARP, and an
430			appropriate updelay setting may be required.
432		follow or 2
434			The "follow" fail_over_mac policy causes the MAC
435			address of the bond to be selected normally (normally
436			the MAC address of the first slave added to the bond).
437			However, the second and subsequent slaves are not set
438			to this MAC address while they are in a backup role; a
439			slave is programmed with the bond's MAC address at
440			failover time (and the formerly active slave receives
441			the newly active slave's MAC address).
443			This policy is useful for multiport devices that
444			either become confused or incur a performance penalty
445			when multiple ports are programmed with the same MAC
446			address.
449		The default policy is none, unless the first slave cannot
450		change its MAC address, in which case the active policy is
451		selected by default.
453		This option may be modified via sysfs only when no slaves are
454		present in the bond.
456		This option was added in bonding version 3.2.0.  The "follow"
457		policy was added in bonding version 3.3.0.
459	lacp_rate
461		Option specifying the rate in which we'll ask our link partner
462		to transmit LACPDU packets in 802.3ad mode.  Possible values
463		are:
465		slow or 0
466			Request partner to transmit LACPDUs every 30 seconds
468		fast or 1
469			Request partner to transmit LACPDUs every 1 second
471		The default is slow.
473	max_bonds
475		Specifies the number of bonding devices to create for this
476		instance of the bonding driver.  E.g., if max_bonds is 3, and
477		the bonding driver is not already loaded, then bond0, bond1
478		and bond2 will be created.  The default value is 1.  Specifying
479		a value of 0 will load bonding, but will not create any devices.
481	miimon
483		Specifies the MII link monitoring frequency in milliseconds.
484		This determines how often the link state of each slave is
485		inspected for link failures.  A value of zero disables MII
486		link monitoring.  A value of 100 is a good starting point.
487		The use_carrier option, below, affects how the link state is
488		determined.  See the High Availability section for additional
489		information.  The default value is 0.
491	min_links
493		Specifies the minimum number of links that must be active before
494		asserting carrier. It is similar to the Cisco EtherChannel min-links
495		feature. This allows setting the minimum number of member ports that
496		must be up (link-up state) before marking the bond device as up
497		(carrier on). This is useful for situations where higher level services
498		such as clustering want to ensure a minimum number of low bandwidth
499		links are active before switchover. This option only affect 802.3ad
500		mode.
502		The default value is 0. This will cause carrier to be asserted (for
503		802.3ad mode) whenever there is an active aggregator, regardless of the
504		number of available links in that aggregator. Note that, because an
505		aggregator cannot be active without at least one available link,
506		setting this option to 0 or to 1 has the exact same effect.
508	mode
510		Specifies one of the bonding policies. The default is
511		balance-rr (round robin).  Possible values are:
513		balance-rr or 0
515			Round-robin policy: Transmit packets in sequential
516			order from the first available slave through the
517			last.  This mode provides load balancing and fault
518			tolerance.
520		active-backup or 1
522			Active-backup policy: Only one slave in the bond is
523			active.  A different slave becomes active if, and only
524			if, the active slave fails.  The bond's MAC address is
525			externally visible on only one port (network adapter)
526			to avoid confusing the switch.
528			In bonding version 2.6.2 or later, when a failover
529			occurs in active-backup mode, bonding will issue one
530			or more gratuitous ARPs on the newly active slave.
531			One gratuitous ARP is issued for the bonding master
532			interface and each VLAN interfaces configured above
533			it, provided that the interface has at least one IP
534			address configured.  Gratuitous ARPs issued for VLAN
535			interfaces are tagged with the appropriate VLAN id.
537			This mode provides fault tolerance.  The primary
538			option, documented below, affects the behavior of this
539			mode.
541		balance-xor or 2
543			XOR policy: Transmit based on the selected transmit
544			hash policy.  The default policy is a simple [(source
545			MAC address XOR'd with destination MAC address) modulo
546			slave count].  Alternate transmit policies may be
547			selected via the xmit_hash_policy option, described
548			below.
550			This mode provides load balancing and fault tolerance.
552		broadcast or 3
554			Broadcast policy: transmits everything on all slave
555			interfaces.  This mode provides fault tolerance.
557		802.3ad or 4
559			IEEE 802.3ad Dynamic link aggregation.  Creates
560			aggregation groups that share the same speed and
561			duplex settings.  Utilizes all slaves in the active
562			aggregator according to the 802.3ad specification.
564			Slave selection for outgoing traffic is done according
565			to the transmit hash policy, which may be changed from
566			the default simple XOR policy via the xmit_hash_policy
567			option, documented below.  Note that not all transmit
568			policies may be 802.3ad compliant, particularly in
569			regards to the packet mis-ordering requirements of
570			section 43.2.4 of the 802.3ad standard.  Differing
571			peer implementations will have varying tolerances for
572			noncompliance.
574			Prerequisites:
576			1. Ethtool support in the base drivers for retrieving
577			the speed and duplex of each slave.
579			2. A switch that supports IEEE 802.3ad Dynamic link
580			aggregation.
582			Most switches will require some type of configuration
583			to enable 802.3ad mode.
585		balance-tlb or 5
587			Adaptive transmit load balancing: channel bonding that
588			does not require any special switch support.  The
589			outgoing traffic is distributed according to the
590			current load (computed relative to the speed) on each
591			slave.  Incoming traffic is received by the current
592			slave.  If the receiving slave fails, another slave
593			takes over the MAC address of the failed receiving
594			slave.
596			Prerequisite:
598			Ethtool support in the base drivers for retrieving the
599			speed of each slave.
601		balance-alb or 6
603			Adaptive load balancing: includes balance-tlb plus
604			receive load balancing (rlb) for IPV4 traffic, and
605			does not require any special switch support.  The
606			receive load balancing is achieved by ARP negotiation.
607			The bonding driver intercepts the ARP Replies sent by
608			the local system on their way out and overwrites the
609			source hardware address with the unique hardware
610			address of one of the slaves in the bond such that
611			different peers use different hardware addresses for
612			the server.
614			Receive traffic from connections created by the server
615			is also balanced.  When the local system sends an ARP
616			Request the bonding driver copies and saves the peer's
617			IP information from the ARP packet.  When the ARP
618			Reply arrives from the peer, its hardware address is
619			retrieved and the bonding driver initiates an ARP
620			reply to this peer assigning it to one of the slaves
621			in the bond.  A problematic outcome of using ARP
622			negotiation for balancing is that each time that an
623			ARP request is broadcast it uses the hardware address
624			of the bond.  Hence, peers learn the hardware address
625			of the bond and the balancing of receive traffic
626			collapses to the current slave.  This is handled by
627			sending updates (ARP Replies) to all the peers with
628			their individually assigned hardware address such that
629			the traffic is redistributed.  Receive traffic is also
630			redistributed when a new slave is added to the bond
631			and when an inactive slave is re-activated.  The
632			receive load is distributed sequentially (round robin)
633			among the group of highest speed slaves in the bond.
635			When a link is reconnected or a new slave joins the
636			bond the receive traffic is redistributed among all
637			active slaves in the bond by initiating ARP Replies
638			with the selected MAC address to each of the
639			clients. The updelay parameter (detailed below) must
640			be set to a value equal or greater than the switch's
641			forwarding delay so that the ARP Replies sent to the
642			peers will not be blocked by the switch.
644			Prerequisites:
646			1. Ethtool support in the base drivers for retrieving
647			the speed of each slave.
649			2. Base driver support for setting the hardware
650			address of a device while it is open.  This is
651			required so that there will always be one slave in the
652			team using the bond hardware address (the
653			curr_active_slave) while having a unique hardware
654			address for each slave in the bond.  If the
655			curr_active_slave fails its hardware address is
656			swapped with the new curr_active_slave that was
657			chosen.
659	num_grat_arp
660	num_unsol_na
662		Specify the number of peer notifications (gratuitous ARPs and
663		unsolicited IPv6 Neighbor Advertisements) to be issued after a
664		failover event.  As soon as the link is up on the new slave
665		(possibly immediately) a peer notification is sent on the
666		bonding device and each VLAN sub-device.  This is repeated at
667		each link monitor interval (arp_interval or miimon, whichever
668		is active) if the number is greater than 1.
670		The valid range is 0 - 255; the default value is 1.  These options
671		affect only the active-backup mode.  These options were added for
672		bonding versions 3.3.0 and 3.4.0 respectively.
674		From Linux 3.0 and bonding version 3.7.1, these notifications
675		are generated by the ipv4 and ipv6 code and the numbers of
676		repetitions cannot be set independently.
678	packets_per_slave
680		Specify the number of packets to transmit through a slave before
681		moving to the next one. When set to 0 then a slave is chosen at
682		random.
684		The valid range is 0 - 65535; the default value is 1. This option
685		has effect only in balance-rr mode.
687	primary
689		A string (eth0, eth2, etc) specifying which slave is the
690		primary device.  The specified device will always be the
691		active slave while it is available.  Only when the primary is
692		off-line will alternate devices be used.  This is useful when
693		one slave is preferred over another, e.g., when one slave has
694		higher throughput than another.
696		The primary option is only valid for active-backup(1),
697		balance-tlb (5) and balance-alb (6) mode.
699	primary_reselect
701		Specifies the reselection policy for the primary slave.  This
702		affects how the primary slave is chosen to become the active slave
703		when failure of the active slave or recovery of the primary slave
704		occurs.  This option is designed to prevent flip-flopping between
705		the primary slave and other slaves.  Possible values are:
707		always or 0 (default)
709			The primary slave becomes the active slave whenever it
710			comes back up.
712		better or 1
714			The primary slave becomes the active slave when it comes
715			back up, if the speed and duplex of the primary slave is
716			better than the speed and duplex of the current active
717			slave.
719		failure or 2
721			The primary slave becomes the active slave only if the
722			current active slave fails and the primary slave is up.
724		The primary_reselect setting is ignored in two cases:
726			If no slaves are active, the first slave to recover is
727			made the active slave.
729			When initially enslaved, the primary slave is always made
730			the active slave.
732		Changing the primary_reselect policy via sysfs will cause an
733		immediate selection of the best active slave according to the new
734		policy.  This may or may not result in a change of the active
735		slave, depending upon the circumstances.
737		This option was added for bonding version 3.6.0.
739	updelay
741		Specifies the time, in milliseconds, to wait before enabling a
742		slave after a link recovery has been detected.  This option is
743		only valid for the miimon link monitor.  The updelay value
744		should be a multiple of the miimon value; if not, it will be
745		rounded down to the nearest multiple.  The default value is 0.
747	use_carrier
749		Specifies whether or not miimon should use MII or ETHTOOL
750		ioctls vs. netif_carrier_ok() to determine the link
751		status. The MII or ETHTOOL ioctls are less efficient and
752		utilize a deprecated calling sequence within the kernel.  The
753		netif_carrier_ok() relies on the device driver to maintain its
754		state with netif_carrier_on/off; at this writing, most, but
755		not all, device drivers support this facility.
757		If bonding insists that the link is up when it should not be,
758		it may be that your network device driver does not support
759		netif_carrier_on/off.  The default state for netif_carrier is
760		"carrier on," so if a driver does not support netif_carrier,
761		it will appear as if the link is always up.  In this case,
762		setting use_carrier to 0 will cause bonding to revert to the
763		MII / ETHTOOL ioctl method to determine the link state.
765		A value of 1 enables the use of netif_carrier_ok(), a value of
766		0 will use the deprecated MII / ETHTOOL ioctls.  The default
767		value is 1.
769	xmit_hash_policy
771		Selects the transmit hash policy to use for slave selection in
772		balance-xor and 802.3ad modes.  Possible values are:
774		layer2
776			Uses XOR of hardware MAC addresses to generate the
777			hash.  The formula is
779			(source MAC XOR destination MAC) modulo slave count
781			This algorithm will place all traffic to a particular
782			network peer on the same slave.
784			This algorithm is 802.3ad compliant.
786		layer2+3
788			This policy uses a combination of layer2 and layer3
789			protocol information to generate the hash.
791			Uses XOR of hardware MAC addresses and IP addresses to
792			generate the hash.  The formula is
794			hash = source MAC XOR destination MAC
795			hash = hash XOR source IP XOR destination IP
796			hash = hash XOR (hash RSHIFT 16)
797			hash = hash XOR (hash RSHIFT 8)
798			And then hash is reduced modulo slave count.
800			If the protocol is IPv6 then the source and destination
801			addresses are first hashed using ipv6_addr_hash.
803			This algorithm will place all traffic to a particular
804			network peer on the same slave.  For non-IP traffic,
805			the formula is the same as for the layer2 transmit
806			hash policy.
808			This policy is intended to provide a more balanced
809			distribution of traffic than layer2 alone, especially
810			in environments where a layer3 gateway device is
811			required to reach most destinations.
813			This algorithm is 802.3ad compliant.
815		layer3+4
817			This policy uses upper layer protocol information,
818			when available, to generate the hash.  This allows for
819			traffic to a particular network peer to span multiple
820			slaves, although a single connection will not span
821			multiple slaves.
823			The formula for unfragmented TCP and UDP packets is
825			hash = source port, destination port (as in the header)
826			hash = hash XOR source IP XOR destination IP
827			hash = hash XOR (hash RSHIFT 16)
828			hash = hash XOR (hash RSHIFT 8)
829			And then hash is reduced modulo slave count.
831			If the protocol is IPv6 then the source and destination
832			addresses are first hashed using ipv6_addr_hash.
834			For fragmented TCP or UDP packets and all other IPv4 and
835			IPv6 protocol traffic, the source and destination port
836			information is omitted.  For non-IP traffic, the
837			formula is the same as for the layer2 transmit hash
838			policy.
840			This algorithm is not fully 802.3ad compliant.  A
841			single TCP or UDP conversation containing both
842			fragmented and unfragmented packets will see packets
843			striped across two interfaces.  This may result in out
844			of order delivery.  Most traffic types will not meet
845			this criteria, as TCP rarely fragments traffic, and
846			most UDP traffic is not involved in extended
847			conversations.  Other implementations of 802.3ad may
848			or may not tolerate this noncompliance.
850		encap2+3
852			This policy uses the same formula as layer2+3 but it
853			relies on skb_flow_dissect to obtain the header fields
854			which might result in the use of inner headers if an
855			encapsulation protocol is used. For example this will
856			improve the performance for tunnel users because the
857			packets will be distributed according to the encapsulated
858			flows.
860		encap3+4
862			This policy uses the same formula as layer3+4 but it
863			relies on skb_flow_dissect to obtain the header fields
864			which might result in the use of inner headers if an
865			encapsulation protocol is used. For example this will
866			improve the performance for tunnel users because the
867			packets will be distributed according to the encapsulated
868			flows.
870		The default value is layer2.  This option was added in bonding
871		version 2.6.3.  In earlier versions of bonding, this parameter
872		does not exist, and the layer2 policy is the only policy.  The
873		layer2+3 value was added for bonding version 3.2.2.
875	resend_igmp
877		Specifies the number of IGMP membership reports to be issued after
878		a failover event. One membership report is issued immediately after
879		the failover, subsequent packets are sent in each 200ms interval.
881		The valid range is 0 - 255; the default value is 1. A value of 0
882		prevents the IGMP membership report from being issued in response
883		to the failover event.
885		This option is useful for bonding modes balance-rr (0), active-backup
886		(1), balance-tlb (5) and balance-alb (6), in which a failover can
887		switch the IGMP traffic from one slave to another.  Therefore a fresh
888		IGMP report must be issued to cause the switch to forward the incoming
889		IGMP traffic over the newly selected slave.
891		This option was added for bonding version 3.7.0.
893	lp_interval
895		Specifies the number of seconds between instances where the bonding
896		driver sends learning packets to each slaves peer switch.
898		The valid range is 1 - 0x7fffffff; the default value is 1. This Option
899		has effect only in balance-tlb and balance-alb modes.
901	3. Configuring Bonding Devices
902	==============================
904		You can configure bonding using either your distro's network
905	initialization scripts, or manually using either iproute2 or the
906	sysfs interface.  Distros generally use one of three packages for the
907	network initialization scripts: initscripts, sysconfig or interfaces.
908	Recent versions of these packages have support for bonding, while older
909	versions do not.
911		We will first describe the options for configuring bonding for
912	distros using versions of initscripts, sysconfig and interfaces with full
913	or partial support for bonding, then provide information on enabling
914	bonding without support from the network initialization scripts (i.e.,
915	older versions of initscripts or sysconfig).
917		If you're unsure whether your distro uses sysconfig,
918	initscripts or interfaces, or don't know if it's new enough, have no fear.
919	Determining this is fairly straightforward.
921		First, look for a file called interfaces in /etc/network directory.
922	If this file is present in your system, then your system use interfaces. See
923	Configuration with Interfaces Support.
925		Else, issue the command:
927	$ rpm -qf /sbin/ifup
929		It will respond with a line of text starting with either
930	"initscripts" or "sysconfig," followed by some numbers.  This is the
931	package that provides your network initialization scripts.
933		Next, to determine if your installation supports bonding,
934	issue the command:
936	$ grep ifenslave /sbin/ifup
938		If this returns any matches, then your initscripts or
939	sysconfig has support for bonding.
941	3.1 Configuration with Sysconfig Support
942	----------------------------------------
944		This section applies to distros using a version of sysconfig
945	with bonding support, for example, SuSE Linux Enterprise Server 9.
947		SuSE SLES 9's networking configuration system does support
948	bonding, however, at this writing, the YaST system configuration
949	front end does not provide any means to work with bonding devices.
950	Bonding devices can be managed by hand, however, as follows.
952		First, if they have not already been configured, configure the
953	slave devices.  On SLES 9, this is most easily done by running the
954	yast2 sysconfig configuration utility.  The goal is for to create an
955	ifcfg-id file for each slave device.  The simplest way to accomplish
956	this is to configure the devices for DHCP (this is only to get the
957	file ifcfg-id file created; see below for some issues with DHCP).  The
958	name of the configuration file for each device will be of the form:
960	ifcfg-id-xx:xx:xx:xx:xx:xx
962		Where the "xx" portion will be replaced with the digits from
963	the device's permanent MAC address.
965		Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been
966	created, it is necessary to edit the configuration files for the slave
967	devices (the MAC addresses correspond to those of the slave devices).
968	Before editing, the file will contain multiple lines, and will look
969	something like this:
971	BOOTPROTO='dhcp'
972	STARTMODE='on'
973	USERCTL='no'
975	_nm_name='bus-pci-0001:61:01.0'
977		Change the BOOTPROTO and STARTMODE lines to the following:
979	BOOTPROTO='none'
980	STARTMODE='off'
982		Do not alter the UNIQUE or _nm_name lines.  Remove any other
983	lines (USERCTL, etc).
985		Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified,
986	it's time to create the configuration file for the bonding device
987	itself.  This file is named ifcfg-bondX, where X is the number of the
988	bonding device to create, starting at 0.  The first such file is
989	ifcfg-bond0, the second is ifcfg-bond1, and so on.  The sysconfig
990	network configuration system will correctly start multiple instances
991	of bonding.
993		The contents of the ifcfg-bondX file is as follows:
995	BOOTPROTO="static"
997	IPADDR=""
998	NETMASK=""
999	NETWORK=""
1001	STARTMODE="onboot"
1003	BONDING_MODULE_OPTS="mode=active-backup miimon=100"
1004	BONDING_SLAVE0="eth0"
1005	BONDING_SLAVE1="bus-pci-0000:06:08.1"
1007		Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK
1008	values with the appropriate values for your network.
1010		The STARTMODE specifies when the device is brought online.
1011	The possible values are:
1013		onboot:	 The device is started at boot time.  If you're not
1014			 sure, this is probably what you want.
1016		manual:	 The device is started only when ifup is called
1017			 manually.  Bonding devices may be configured this
1018			 way if you do not wish them to start automatically
1019			 at boot for some reason.
1021		hotplug: The device is started by a hotplug event.  This is not
1022			 a valid choice for a bonding device.
1024		off or ignore: The device configuration is ignored.
1026		The line BONDING_MASTER='yes' indicates that the device is a
1027	bonding master device.  The only useful value is "yes."
1029		The contents of BONDING_MODULE_OPTS are supplied to the
1030	instance of the bonding module for this device.  Specify the options
1031	for the bonding mode, link monitoring, and so on here.  Do not include
1032	the max_bonds bonding parameter; this will confuse the configuration
1033	system if you have multiple bonding devices.
1035		Finally, supply one BONDING_SLAVEn="slave device" for each
1036	slave.  where "n" is an increasing value, one for each slave.  The
1037	"slave device" is either an interface name, e.g., "eth0", or a device
1038	specifier for the network device.  The interface name is easier to
1039	find, but the ethN names are subject to change at boot time if, e.g.,
1040	a device early in the sequence has failed.  The device specifiers
1041	(bus-pci-0000:06:08.1 in the example above) specify the physical
1042	network device, and will not change unless the device's bus location
1043	changes (for example, it is moved from one PCI slot to another).  The
1044	example above uses one of each type for demonstration purposes; most
1045	configurations will choose one or the other for all slave devices.
1047		When all configuration files have been modified or created,
1048	networking must be restarted for the configuration changes to take
1049	effect.  This can be accomplished via the following:
1051	# /etc/init.d/network restart
1053		Note that the network control script (/sbin/ifdown) will
1054	remove the bonding module as part of the network shutdown processing,
1055	so it is not necessary to remove the module by hand if, e.g., the
1056	module parameters have changed.
1058		Also, at this writing, YaST/YaST2 will not manage bonding
1059	devices (they do not show bonding interfaces on its list of network
1060	devices).  It is necessary to edit the configuration file by hand to
1061	change the bonding configuration.
1063		Additional general options and details of the ifcfg file
1064	format can be found in an example ifcfg template file:
1066	/etc/sysconfig/network/ifcfg.template
1068		Note that the template does not document the various BONDING_
1069	settings described above, but does describe many of the other options.
1071	3.1.1 Using DHCP with Sysconfig
1072	-------------------------------
1074		Under sysconfig, configuring a device with BOOTPROTO='dhcp'
1075	will cause it to query DHCP for its IP address information.  At this
1076	writing, this does not function for bonding devices; the scripts
1077	attempt to obtain the device address from DHCP prior to adding any of
1078	the slave devices.  Without active slaves, the DHCP requests are not
1079	sent to the network.
1081	3.1.2 Configuring Multiple Bonds with Sysconfig
1082	-----------------------------------------------
1084		The sysconfig network initialization system is capable of
1085	handling multiple bonding devices.  All that is necessary is for each
1086	bonding instance to have an appropriately configured ifcfg-bondX file
1087	(as described above).  Do not specify the "max_bonds" parameter to any
1088	instance of bonding, as this will confuse sysconfig.  If you require
1089	multiple bonding devices with identical parameters, create multiple
1090	ifcfg-bondX files.
1092		Because the sysconfig scripts supply the bonding module
1093	options in the ifcfg-bondX file, it is not necessary to add them to
1094	the system /etc/modules.d/*.conf configuration files.
1096	3.2 Configuration with Initscripts Support
1097	------------------------------------------
1099		This section applies to distros using a recent version of
1100	initscripts with bonding support, for example, Red Hat Enterprise Linux
1101	version 3 or later, Fedora, etc.  On these systems, the network
1102	initialization scripts have knowledge of bonding, and can be configured to
1103	control bonding devices.  Note that older versions of the initscripts
1104	package have lower levels of support for bonding; this will be noted where
1105	applicable.
1107		These distros will not automatically load the network adapter
1108	driver unless the ethX device is configured with an IP address.
1109	Because of this constraint, users must manually configure a
1110	network-script file for all physical adapters that will be members of
1111	a bondX link.  Network script files are located in the directory:
1113	/etc/sysconfig/network-scripts
1115		The file name must be prefixed with "ifcfg-eth" and suffixed
1116	with the adapter's physical adapter number.  For example, the script
1117	for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0.
1118	Place the following text in the file:
1120	DEVICE=eth0
1121	USERCTL=no
1122	ONBOOT=yes
1123	MASTER=bond0
1124	SLAVE=yes
1125	BOOTPROTO=none
1127		The DEVICE= line will be different for every ethX device and
1128	must correspond with the name of the file, i.e., ifcfg-eth1 must have
1129	a device line of DEVICE=eth1.  The setting of the MASTER= line will
1130	also depend on the final bonding interface name chosen for your bond.
1131	As with other network devices, these typically start at 0, and go up
1132	one for each device, i.e., the first bonding instance is bond0, the
1133	second is bond1, and so on.
1135		Next, create a bond network script.  The file name for this
1136	script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is
1137	the number of the bond.  For bond0 the file is named "ifcfg-bond0",
1138	for bond1 it is named "ifcfg-bond1", and so on.  Within that file,
1139	place the following text:
1141	DEVICE=bond0
1142	IPADDR=
1146	ONBOOT=yes
1147	BOOTPROTO=none
1148	USERCTL=no
1150		Be sure to change the networking specific lines (IPADDR,
1151	NETMASK, NETWORK and BROADCAST) to match your network configuration.
1153		For later versions of initscripts, such as that found with Fedora
1154	7 (or later) and Red Hat Enterprise Linux version 5 (or later), it is possible,
1155	and, indeed, preferable, to specify the bonding options in the ifcfg-bond0
1156	file, e.g. a line of the format:
1158	BONDING_OPTS="mode=active-backup arp_interval=60 arp_ip_target="
1160		will configure the bond with the specified options.  The options
1161	specified in BONDING_OPTS are identical to the bonding module parameters
1162	except for the arp_ip_target field when using versions of initscripts older
1163	than and 8.57 (Fedora 8) and 8.45.19 (Red Hat Enterprise Linux 5.2).  When
1164	using older versions each target should be included as a separate option and
1165	should be preceded by a '+' to indicate it should be added to the list of
1166	queried targets, e.g.,
1168		arp_ip_target=+ arp_ip_target=+
1170		is the proper syntax to specify multiple targets.  When specifying
1171	options via BONDING_OPTS, it is not necessary to edit /etc/modprobe.d/*.conf.
1173		For even older versions of initscripts that do not support
1174	BONDING_OPTS, it is necessary to edit /etc/modprobe.d/*.conf, depending upon
1175	your distro) to load the bonding module with your desired options when the
1176	bond0 interface is brought up.  The following lines in /etc/modprobe.d/*.conf
1177	will load the bonding module, and select its options:
1179	alias bond0 bonding
1180	options bond0 mode=balance-alb miimon=100
1182		Replace the sample parameters with the appropriate set of
1183	options for your configuration.
1185		Finally run "/etc/rc.d/init.d/network restart" as root.  This
1186	will restart the networking subsystem and your bond link should be now
1187	up and running.
1189	3.2.1 Using DHCP with Initscripts
1190	---------------------------------
1192		Recent versions of initscripts (the versions supplied with Fedora
1193	Core 3 and Red Hat Enterprise Linux 4, or later versions, are reported to
1194	work) have support for assigning IP information to bonding devices via
1195	DHCP.
1197		To configure bonding for DHCP, configure it as described
1198	above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp"
1199	and add a line consisting of "TYPE=Bonding".  Note that the TYPE value
1200	is case sensitive.
1202	3.2.2 Configuring Multiple Bonds with Initscripts
1203	-------------------------------------------------
1205		Initscripts packages that are included with Fedora 7 and Red Hat
1206	Enterprise Linux 5 support multiple bonding interfaces by simply
1207	specifying the appropriate BONDING_OPTS= in ifcfg-bondX where X is the
1208	number of the bond.  This support requires sysfs support in the kernel,
1209	and a bonding driver of version 3.0.0 or later.  Other configurations may
1210	not support this method for specifying multiple bonding interfaces; for
1211	those instances, see the "Configuring Multiple Bonds Manually" section,
1212	below.
1214	3.3 Configuring Bonding Manually with iproute2
1215	-----------------------------------------------
1217		This section applies to distros whose network initialization
1218	scripts (the sysconfig or initscripts package) do not have specific
1219	knowledge of bonding.  One such distro is SuSE Linux Enterprise Server
1220	version 8.
1222		The general method for these systems is to place the bonding
1223	module parameters into a config file in /etc/modprobe.d/ (as
1224	appropriate for the installed distro), then add modprobe and/or
1225	`ip link` commands to the system's global init script.  The name of
1226	the global init script differs; for sysconfig, it is
1227	/etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local.
1229		For example, if you wanted to make a simple bond of two e100
1230	devices (presumed to be eth0 and eth1), and have it persist across
1231	reboots, edit the appropriate file (/etc/init.d/boot.local or
1232	/etc/rc.d/rc.local), and add the following:
1234	modprobe bonding mode=balance-alb miimon=100
1235	modprobe e100
1236	ifconfig bond0 netmask up
1237	ip link set eth0 master bond0
1238	ip link set eth1 master bond0
1240		Replace the example bonding module parameters and bond0
1241	network configuration (IP address, netmask, etc) with the appropriate
1242	values for your configuration.
1244		Unfortunately, this method will not provide support for the
1245	ifup and ifdown scripts on the bond devices.  To reload the bonding
1246	configuration, it is necessary to run the initialization script, e.g.,
1248	# /etc/init.d/boot.local
1250		or
1252	# /etc/rc.d/rc.local
1254		It may be desirable in such a case to create a separate script
1255	which only initializes the bonding configuration, then call that
1256	separate script from within boot.local.  This allows for bonding to be
1257	enabled without re-running the entire global init script.
1259		To shut down the bonding devices, it is necessary to first
1260	mark the bonding device itself as being down, then remove the
1261	appropriate device driver modules.  For our example above, you can do
1262	the following:
1264	# ifconfig bond0 down
1265	# rmmod bonding
1266	# rmmod e100
1268		Again, for convenience, it may be desirable to create a script
1269	with these commands.
1272	3.3.1 Configuring Multiple Bonds Manually
1273	-----------------------------------------
1275		This section contains information on configuring multiple
1276	bonding devices with differing options for those systems whose network
1277	initialization scripts lack support for configuring multiple bonds.
1279		If you require multiple bonding devices, but all with the same
1280	options, you may wish to use the "max_bonds" module parameter,
1281	documented above.
1283		To create multiple bonding devices with differing options, it is
1284	preferable to use bonding parameters exported by sysfs, documented in the
1285	section below.
1287		For versions of bonding without sysfs support, the only means to
1288	provide multiple instances of bonding with differing options is to load
1289	the bonding driver multiple times.  Note that current versions of the
1290	sysconfig network initialization scripts handle this automatically; if
1291	your distro uses these scripts, no special action is needed.  See the
1292	section Configuring Bonding Devices, above, if you're not sure about your
1293	network initialization scripts.
1295		To load multiple instances of the module, it is necessary to
1296	specify a different name for each instance (the module loading system
1297	requires that every loaded module, even multiple instances of the same
1298	module, have a unique name).  This is accomplished by supplying multiple
1299	sets of bonding options in /etc/modprobe.d/*.conf, for example:
1301	alias bond0 bonding
1302	options bond0 -o bond0 mode=balance-rr miimon=100
1304	alias bond1 bonding
1305	options bond1 -o bond1 mode=balance-alb miimon=50
1307		will load the bonding module two times.  The first instance is
1308	named "bond0" and creates the bond0 device in balance-rr mode with an
1309	miimon of 100.  The second instance is named "bond1" and creates the
1310	bond1 device in balance-alb mode with an miimon of 50.
1312		In some circumstances (typically with older distributions),
1313	the above does not work, and the second bonding instance never sees
1314	its options.  In that case, the second options line can be substituted
1315	as follows:
1317	install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \
1318		mode=balance-alb miimon=50
1320		This may be repeated any number of times, specifying a new and
1321	unique name in place of bond1 for each subsequent instance.
1323		It has been observed that some Red Hat supplied kernels are unable
1324	to rename modules at load time (the "-o bond1" part).  Attempts to pass
1325	that option to modprobe will produce an "Operation not permitted" error.
1326	This has been reported on some Fedora Core kernels, and has been seen on
1327	RHEL 4 as well.  On kernels exhibiting this problem, it will be impossible
1328	to configure multiple bonds with differing parameters (as they are older
1329	kernels, and also lack sysfs support).
1331	3.4 Configuring Bonding Manually via Sysfs
1332	------------------------------------------
1334		Starting with version 3.0.0, Channel Bonding may be configured
1335	via the sysfs interface.  This interface allows dynamic configuration
1336	of all bonds in the system without unloading the module.  It also
1337	allows for adding and removing bonds at runtime.  Ifenslave is no
1338	longer required, though it is still supported.
1340		Use of the sysfs interface allows you to use multiple bonds
1341	with different configurations without having to reload the module.
1342	It also allows you to use multiple, differently configured bonds when
1343	bonding is compiled into the kernel.
1345		You must have the sysfs filesystem mounted to configure
1346	bonding this way.  The examples in this document assume that you
1347	are using the standard mount point for sysfs, e.g. /sys.  If your
1348	sysfs filesystem is mounted elsewhere, you will need to adjust the
1349	example paths accordingly.
1351	Creating and Destroying Bonds
1352	-----------------------------
1353	To add a new bond foo:
1354	# echo +foo > /sys/class/net/bonding_masters
1356	To remove an existing bond bar:
1357	# echo -bar > /sys/class/net/bonding_masters
1359	To show all existing bonds:
1360	# cat /sys/class/net/bonding_masters
1362	NOTE: due to 4K size limitation of sysfs files, this list may be
1363	truncated if you have more than a few hundred bonds.  This is unlikely
1364	to occur under normal operating conditions.
1366	Adding and Removing Slaves
1367	--------------------------
1368		Interfaces may be enslaved to a bond using the file
1369	/sys/class/net/<bond>/bonding/slaves.  The semantics for this file
1370	are the same as for the bonding_masters file.
1372	To enslave interface eth0 to bond bond0:
1373	# ifconfig bond0 up
1374	# echo +eth0 > /sys/class/net/bond0/bonding/slaves
1376	To free slave eth0 from bond bond0:
1377	# echo -eth0 > /sys/class/net/bond0/bonding/slaves
1379		When an interface is enslaved to a bond, symlinks between the
1380	two are created in the sysfs filesystem.  In this case, you would get
1381	/sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and
1382	/sys/class/net/eth0/master pointing to /sys/class/net/bond0.
1384		This means that you can tell quickly whether or not an
1385	interface is enslaved by looking for the master symlink.  Thus:
1386	# echo -eth0 > /sys/class/net/eth0/master/bonding/slaves
1387	will free eth0 from whatever bond it is enslaved to, regardless of
1388	the name of the bond interface.
1390	Changing a Bond's Configuration
1391	-------------------------------
1392		Each bond may be configured individually by manipulating the
1393	files located in /sys/class/net/<bond name>/bonding
1395		The names of these files correspond directly with the command-
1396	line parameters described elsewhere in this file, and, with the
1397	exception of arp_ip_target, they accept the same values.  To see the
1398	current setting, simply cat the appropriate file.
1400		A few examples will be given here; for specific usage
1401	guidelines for each parameter, see the appropriate section in this
1402	document.
1404	To configure bond0 for balance-alb mode:
1405	# ifconfig bond0 down
1406	# echo 6 > /sys/class/net/bond0/bonding/mode
1407	 - or -
1408	# echo balance-alb > /sys/class/net/bond0/bonding/mode
1409		NOTE: The bond interface must be down before the mode can be
1410	changed.
1412	To enable MII monitoring on bond0 with a 1 second interval:
1413	# echo 1000 > /sys/class/net/bond0/bonding/miimon
1414		NOTE: If ARP monitoring is enabled, it will disabled when MII
1415	monitoring is enabled, and vice-versa.
1417	To add ARP targets:
1418	# echo + > /sys/class/net/bond0/bonding/arp_ip_target
1419	# echo + > /sys/class/net/bond0/bonding/arp_ip_target
1420		NOTE:  up to 16 target addresses may be specified.
1422	To remove an ARP target:
1423	# echo - > /sys/class/net/bond0/bonding/arp_ip_target
1425	To configure the interval between learning packet transmits:
1426	# echo 12 > /sys/class/net/bond0/bonding/lp_interval
1427		NOTE: the lp_inteval is the number of seconds between instances where
1428	the bonding driver sends learning packets to each slaves peer switch.  The
1429	default interval is 1 second.
1431	Example Configuration
1432	---------------------
1433		We begin with the same example that is shown in section 3.3,
1434	executed with sysfs, and without using ifenslave.
1436		To make a simple bond of two e100 devices (presumed to be eth0
1437	and eth1), and have it persist across reboots, edit the appropriate
1438	file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the
1439	following:
1441	modprobe bonding
1442	modprobe e100
1443	echo balance-alb > /sys/class/net/bond0/bonding/mode
1444	ifconfig bond0 netmask up
1445	echo 100 > /sys/class/net/bond0/bonding/miimon
1446	echo +eth0 > /sys/class/net/bond0/bonding/slaves
1447	echo +eth1 > /sys/class/net/bond0/bonding/slaves
1449		To add a second bond, with two e1000 interfaces in
1450	active-backup mode, using ARP monitoring, add the following lines to
1451	your init script:
1453	modprobe e1000
1454	echo +bond1 > /sys/class/net/bonding_masters
1455	echo active-backup > /sys/class/net/bond1/bonding/mode
1456	ifconfig bond1 netmask up
1457	echo + /sys/class/net/bond1/bonding/arp_ip_target
1458	echo 2000 > /sys/class/net/bond1/bonding/arp_interval
1459	echo +eth2 > /sys/class/net/bond1/bonding/slaves
1460	echo +eth3 > /sys/class/net/bond1/bonding/slaves
1462	3.5 Configuration with Interfaces Support
1463	-----------------------------------------
1465	        This section applies to distros which use /etc/network/interfaces file
1466	to describe network interface configuration, most notably Debian and it's
1467	derivatives.
1469		The ifup and ifdown commands on Debian don't support bonding out of
1470	the box. The ifenslave-2.6 package should be installed to provide bonding
1471	support.  Once installed, this package will provide bond-* options to be used
1472	into /etc/network/interfaces.
1474		Note that ifenslave-2.6 package will load the bonding module and use
1475	the ifenslave command when appropriate.
1477	Example Configurations
1478	----------------------
1480	In /etc/network/interfaces, the following stanza will configure bond0, in
1481	active-backup mode, with eth0 and eth1 as slaves.
1483	auto bond0
1484	iface bond0 inet dhcp
1485		bond-slaves eth0 eth1
1486		bond-mode active-backup
1487		bond-miimon 100
1488		bond-primary eth0 eth1
1490	If the above configuration doesn't work, you might have a system using
1491	upstart for system startup. This is most notably true for recent
1492	Ubuntu versions. The following stanza in /etc/network/interfaces will
1493	produce the same result on those systems.
1495	auto bond0
1496	iface bond0 inet dhcp
1497		bond-slaves none
1498		bond-mode active-backup
1499		bond-miimon 100
1501	auto eth0
1502	iface eth0 inet manual
1503		bond-master bond0
1504		bond-primary eth0 eth1
1506	auto eth1
1507	iface eth1 inet manual
1508		bond-master bond0
1509		bond-primary eth0 eth1
1511	For a full list of bond-* supported options in /etc/network/interfaces and some
1512	more advanced examples tailored to you particular distros, see the files in
1513	/usr/share/doc/ifenslave-2.6.
1515	3.6 Overriding Configuration for Special Cases
1516	----------------------------------------------
1518	When using the bonding driver, the physical port which transmits a frame is
1519	typically selected by the bonding driver, and is not relevant to the user or
1520	system administrator.  The output port is simply selected using the policies of
1521	the selected bonding mode.  On occasion however, it is helpful to direct certain
1522	classes of traffic to certain physical interfaces on output to implement
1523	slightly more complex policies.  For example, to reach a web server over a
1524	bonded interface in which eth0 connects to a private network, while eth1
1525	connects via a public network, it may be desirous to bias the bond to send said
1526	traffic over eth0 first, using eth1 only as a fall back, while all other traffic
1527	can safely be sent over either interface.  Such configurations may be achieved
1528	using the traffic control utilities inherent in linux.
1530	By default the bonding driver is multiqueue aware and 16 queues are created
1531	when the driver initializes (see Documentation/networking/multiqueue.txt
1532	for details).  If more or less queues are desired the module parameter
1533	tx_queues can be used to change this value.  There is no sysfs parameter
1534	available as the allocation is done at module init time.
1536	The output of the file /proc/net/bonding/bondX has changed so the output Queue
1537	ID is now printed for each slave:
1539	Bonding Mode: fault-tolerance (active-backup)
1540	Primary Slave: None
1541	Currently Active Slave: eth0
1542	MII Status: up
1543	MII Polling Interval (ms): 0
1544	Up Delay (ms): 0
1545	Down Delay (ms): 0
1547	Slave Interface: eth0
1548	MII Status: up
1549	Link Failure Count: 0
1550	Permanent HW addr: 00:1a:a0:12:8f:cb
1551	Slave queue ID: 0
1553	Slave Interface: eth1
1554	MII Status: up
1555	Link Failure Count: 0
1556	Permanent HW addr: 00:1a:a0:12:8f:cc
1557	Slave queue ID: 2
1559	The queue_id for a slave can be set using the command:
1561	# echo "eth1:2" > /sys/class/net/bond0/bonding/queue_id
1563	Any interface that needs a queue_id set should set it with multiple calls
1564	like the one above until proper priorities are set for all interfaces.  On
1565	distributions that allow configuration via initscripts, multiple 'queue_id'
1566	arguments can be added to BONDING_OPTS to set all needed slave queues.
1568	These queue id's can be used in conjunction with the tc utility to configure
1569	a multiqueue qdisc and filters to bias certain traffic to transmit on certain
1570	slave devices.  For instance, say we wanted, in the above configuration to
1571	force all traffic bound to to use eth1 in the bond as its output
1572	device. The following commands would accomplish this:
1574	# tc qdisc add dev bond0 handle 1 root multiq
1576	# tc filter add dev bond0 protocol ip parent 1: prio 1 u32 match ip dst \
1577 action skbedit queue_mapping 2
1579	These commands tell the kernel to attach a multiqueue queue discipline to the
1580	bond0 interface and filter traffic enqueued to it, such that packets with a dst
1581	ip of have their output queue mapping value overwritten to 2.
1582	This value is then passed into the driver, causing the normal output path
1583	selection policy to be overridden, selecting instead qid 2, which maps to eth1.
1585	Note that qid values begin at 1.  Qid 0 is reserved to initiate to the driver
1586	that normal output policy selection should take place.  One benefit to simply
1587	leaving the qid for a slave to 0 is the multiqueue awareness in the bonding
1588	driver that is now present.  This awareness allows tc filters to be placed on
1589	slave devices as well as bond devices and the bonding driver will simply act as
1590	a pass-through for selecting output queues on the slave device rather than 
1591	output port selection.
1593	This feature first appeared in bonding driver version 3.7.0 and support for
1594	output slave selection was limited to round-robin and active-backup modes.
1596	4 Querying Bonding Configuration
1597	=================================
1599	4.1 Bonding Configuration
1600	-------------------------
1602		Each bonding device has a read-only file residing in the
1603	/proc/net/bonding directory.  The file contents include information
1604	about the bonding configuration, options and state of each slave.
1606		For example, the contents of /proc/net/bonding/bond0 after the
1607	driver is loaded with parameters of mode=0 and miimon=1000 is
1608	generally as follows:
1610		Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004)
1611	        Bonding Mode: load balancing (round-robin)
1612	        Currently Active Slave: eth0
1613	        MII Status: up
1614	        MII Polling Interval (ms): 1000
1615	        Up Delay (ms): 0
1616	        Down Delay (ms): 0
1618	        Slave Interface: eth1
1619	        MII Status: up
1620	        Link Failure Count: 1
1622	        Slave Interface: eth0
1623	        MII Status: up
1624	        Link Failure Count: 1
1626		The precise format and contents will change depending upon the
1627	bonding configuration, state, and version of the bonding driver.
1629	4.2 Network configuration
1630	-------------------------
1632		The network configuration can be inspected using the ifconfig
1633	command.  Bonding devices will have the MASTER flag set; Bonding slave
1634	devices will have the SLAVE flag set.  The ifconfig output does not
1635	contain information on which slaves are associated with which masters.
1637		In the example below, the bond0 interface is the master
1638	(MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of
1639	bond0 have the same MAC address (HWaddr) as bond0 for all modes except
1640	TLB and ALB that require a unique MAC address for each slave.
1642	# /sbin/ifconfig
1643	bond0     Link encap:Ethernet  HWaddr 00:C0:F0:1F:37:B4
1644	          inet addr:XXX.XXX.XXX.YYY  Bcast:XXX.XXX.XXX.255  Mask:
1646	          RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0
1647	          TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0
1648	          collisions:0 txqueuelen:0
1650	eth0      Link encap:Ethernet  HWaddr 00:C0:F0:1F:37:B4
1652	          RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0
1653	          TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0
1654	          collisions:0 txqueuelen:100
1655	          Interrupt:10 Base address:0x1080
1657	eth1      Link encap:Ethernet  HWaddr 00:C0:F0:1F:37:B4
1659	          RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0
1660	          TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0
1661	          collisions:0 txqueuelen:100
1662	          Interrupt:9 Base address:0x1400
1664	5. Switch Configuration
1665	=======================
1667		For this section, "switch" refers to whatever system the
1668	bonded devices are directly connected to (i.e., where the other end of
1669	the cable plugs into).  This may be an actual dedicated switch device,
1670	or it may be another regular system (e.g., another computer running
1671	Linux),
1673		The active-backup, balance-tlb and balance-alb modes do not
1674	require any specific configuration of the switch.
1676		The 802.3ad mode requires that the switch have the appropriate
1677	ports configured as an 802.3ad aggregation.  The precise method used
1678	to configure this varies from switch to switch, but, for example, a
1679	Cisco 3550 series switch requires that the appropriate ports first be
1680	grouped together in a single etherchannel instance, then that
1681	etherchannel is set to mode "lacp" to enable 802.3ad (instead of
1682	standard EtherChannel).
1684		The balance-rr, balance-xor and broadcast modes generally
1685	require that the switch have the appropriate ports grouped together.
1686	The nomenclature for such a group differs between switches, it may be
1687	called an "etherchannel" (as in the Cisco example, above), a "trunk
1688	group" or some other similar variation.  For these modes, each switch
1689	will also have its own configuration options for the switch's transmit
1690	policy to the bond.  Typical choices include XOR of either the MAC or
1691	IP addresses.  The transmit policy of the two peers does not need to
1692	match.  For these three modes, the bonding mode really selects a
1693	transmit policy for an EtherChannel group; all three will interoperate
1694	with another EtherChannel group.
1697	6. 802.1q VLAN Support
1698	======================
1700		It is possible to configure VLAN devices over a bond interface
1701	using the 8021q driver.  However, only packets coming from the 8021q
1702	driver and passing through bonding will be tagged by default.  Self
1703	generated packets, for example, bonding's learning packets or ARP
1704	packets generated by either ALB mode or the ARP monitor mechanism, are
1705	tagged internally by bonding itself.  As a result, bonding must
1706	"learn" the VLAN IDs configured above it, and use those IDs to tag
1707	self generated packets.
1709		For reasons of simplicity, and to support the use of adapters
1710	that can do VLAN hardware acceleration offloading, the bonding
1711	interface declares itself as fully hardware offloading capable, it gets
1712	the add_vid/kill_vid notifications to gather the necessary
1713	information, and it propagates those actions to the slaves.  In case
1714	of mixed adapter types, hardware accelerated tagged packets that
1715	should go through an adapter that is not offloading capable are
1716	"un-accelerated" by the bonding driver so the VLAN tag sits in the
1717	regular location.
1719		VLAN interfaces *must* be added on top of a bonding interface
1720	only after enslaving at least one slave.  The bonding interface has a
1721	hardware address of 00:00:00:00:00:00 until the first slave is added.
1722	If the VLAN interface is created prior to the first enslavement, it
1723	would pick up the all-zeroes hardware address.  Once the first slave
1724	is attached to the bond, the bond device itself will pick up the
1725	slave's hardware address, which is then available for the VLAN device.
1727		Also, be aware that a similar problem can occur if all slaves
1728	are released from a bond that still has one or more VLAN interfaces on
1729	top of it.  When a new slave is added, the bonding interface will
1730	obtain its hardware address from the first slave, which might not
1731	match the hardware address of the VLAN interfaces (which was
1732	ultimately copied from an earlier slave).
1734		There are two methods to insure that the VLAN device operates
1735	with the correct hardware address if all slaves are removed from a
1736	bond interface:
1738		1. Remove all VLAN interfaces then recreate them
1740		2. Set the bonding interface's hardware address so that it
1741	matches the hardware address of the VLAN interfaces.
1743		Note that changing a VLAN interface's HW address would set the
1744	underlying device -- i.e. the bonding interface -- to promiscuous
1745	mode, which might not be what you want.
1748	7. Link Monitoring
1749	==================
1751		The bonding driver at present supports two schemes for
1752	monitoring a slave device's link state: the ARP monitor and the MII
1753	monitor.
1755		At the present time, due to implementation restrictions in the
1756	bonding driver itself, it is not possible to enable both ARP and MII
1757	monitoring simultaneously.
1759	7.1 ARP Monitor Operation
1760	-------------------------
1762		The ARP monitor operates as its name suggests: it sends ARP
1763	queries to one or more designated peer systems on the network, and
1764	uses the response as an indication that the link is operating.  This
1765	gives some assurance that traffic is actually flowing to and from one
1766	or more peers on the local network.
1768		The ARP monitor relies on the device driver itself to verify
1769	that traffic is flowing.  In particular, the driver must keep up to
1770	date the last receive time, dev->last_rx, and transmit start time,
1771	dev->trans_start.  If these are not updated by the driver, then the
1772	ARP monitor will immediately fail any slaves using that driver, and
1773	those slaves will stay down.  If networking monitoring (tcpdump, etc)
1774	shows the ARP requests and replies on the network, then it may be that
1775	your device driver is not updating last_rx and trans_start.
1777	7.2 Configuring Multiple ARP Targets
1778	------------------------------------
1780		While ARP monitoring can be done with just one target, it can
1781	be useful in a High Availability setup to have several targets to
1782	monitor.  In the case of just one target, the target itself may go
1783	down or have a problem making it unresponsive to ARP requests.  Having
1784	an additional target (or several) increases the reliability of the ARP
1785	monitoring.
1787		Multiple ARP targets must be separated by commas as follows:
1789	# example options for ARP monitoring with three targets
1790	alias bond0 bonding
1791	options bond0 arp_interval=60 arp_ip_target=,,
1793		For just a single target the options would resemble:
1795	# example options for ARP monitoring with one target
1796	alias bond0 bonding
1797	options bond0 arp_interval=60 arp_ip_target=
1800	7.3 MII Monitor Operation
1801	-------------------------
1803		The MII monitor monitors only the carrier state of the local
1804	network interface.  It accomplishes this in one of three ways: by
1805	depending upon the device driver to maintain its carrier state, by
1806	querying the device's MII registers, or by making an ethtool query to
1807	the device.
1809		If the use_carrier module parameter is 1 (the default value),
1810	then the MII monitor will rely on the driver for carrier state
1811	information (via the netif_carrier subsystem).  As explained in the
1812	use_carrier parameter information, above, if the MII monitor fails to
1813	detect carrier loss on the device (e.g., when the cable is physically
1814	disconnected), it may be that the driver does not support
1815	netif_carrier.
1817		If use_carrier is 0, then the MII monitor will first query the
1818	device's (via ioctl) MII registers and check the link state.  If that
1819	request fails (not just that it returns carrier down), then the MII
1820	monitor will make an ethtool ETHOOL_GLINK request to attempt to obtain
1821	the same information.  If both methods fail (i.e., the driver either
1822	does not support or had some error in processing both the MII register
1823	and ethtool requests), then the MII monitor will assume the link is
1824	up.
1826	8. Potential Sources of Trouble
1827	===============================
1829	8.1 Adventures in Routing
1830	-------------------------
1832		When bonding is configured, it is important that the slave
1833	devices not have routes that supersede routes of the master (or,
1834	generally, not have routes at all).  For example, suppose the bonding
1835	device bond0 has two slaves, eth0 and eth1, and the routing table is
1836	as follows:
1838	Kernel IP routing table
1839	Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
1840     U        40 0          0 eth0
1841     U        40 0          0 eth1
1842     U        40 0          0 bond0
1843       U        40 0          0 lo
1845		This routing configuration will likely still update the
1846	receive/transmit times in the driver (needed by the ARP monitor), but
1847	may bypass the bonding driver (because outgoing traffic to, in this
1848	case, another host on network 10 would use eth0 or eth1 before bond0).
1850		The ARP monitor (and ARP itself) may become confused by this
1851	configuration, because ARP requests (generated by the ARP monitor)
1852	will be sent on one interface (bond0), but the corresponding reply
1853	will arrive on a different interface (eth0).  This reply looks to ARP
1854	as an unsolicited ARP reply (because ARP matches replies on an
1855	interface basis), and is discarded.  The MII monitor is not affected
1856	by the state of the routing table.
1858		The solution here is simply to insure that slaves do not have
1859	routes of their own, and if for some reason they must, those routes do
1860	not supersede routes of their master.  This should generally be the
1861	case, but unusual configurations or errant manual or automatic static
1862	route additions may cause trouble.
1864	8.2 Ethernet Device Renaming
1865	----------------------------
1867		On systems with network configuration scripts that do not
1868	associate physical devices directly with network interface names (so
1869	that the same physical device always has the same "ethX" name), it may
1870	be necessary to add some special logic to config files in
1871	/etc/modprobe.d/.
1873		For example, given a modules.conf containing the following:
1875	alias bond0 bonding
1876	options bond0 mode=some-mode miimon=50
1877	alias eth0 tg3
1878	alias eth1 tg3
1879	alias eth2 e1000
1880	alias eth3 e1000
1882		If neither eth0 and eth1 are slaves to bond0, then when the
1883	bond0 interface comes up, the devices may end up reordered.  This
1884	happens because bonding is loaded first, then its slave device's
1885	drivers are loaded next.  Since no other drivers have been loaded,
1886	when the e1000 driver loads, it will receive eth0 and eth1 for its
1887	devices, but the bonding configuration tries to enslave eth2 and eth3
1888	(which may later be assigned to the tg3 devices).
1890		Adding the following:
1892	add above bonding e1000 tg3
1894		causes modprobe to load e1000 then tg3, in that order, when
1895	bonding is loaded.  This command is fully documented in the
1896	modules.conf manual page.
1898		On systems utilizing modprobe an equivalent problem can occur.
1899	In this case, the following can be added to config files in
1900	/etc/modprobe.d/ as:
1902	softdep bonding pre: tg3 e1000
1904		This will load tg3 and e1000 modules before loading the bonding one.
1905	Full documentation on this can be found in the modprobe.d and modprobe
1906	manual pages.
1908	8.3. Painfully Slow Or No Failed Link Detection By Miimon
1909	---------------------------------------------------------
1911		By default, bonding enables the use_carrier option, which
1912	instructs bonding to trust the driver to maintain carrier state.
1914		As discussed in the options section, above, some drivers do
1915	not support the netif_carrier_on/_off link state tracking system.
1916	With use_carrier enabled, bonding will always see these links as up,
1917	regardless of their actual state.
1919		Additionally, other drivers do support netif_carrier, but do
1920	not maintain it in real time, e.g., only polling the link state at
1921	some fixed interval.  In this case, miimon will detect failures, but
1922	only after some long period of time has expired.  If it appears that
1923	miimon is very slow in detecting link failures, try specifying
1924	use_carrier=0 to see if that improves the failure detection time.  If
1925	it does, then it may be that the driver checks the carrier state at a
1926	fixed interval, but does not cache the MII register values (so the
1927	use_carrier=0 method of querying the registers directly works).  If
1928	use_carrier=0 does not improve the failover, then the driver may cache
1929	the registers, or the problem may be elsewhere.
1931		Also, remember that miimon only checks for the device's
1932	carrier state.  It has no way to determine the state of devices on or
1933	beyond other ports of a switch, or if a switch is refusing to pass
1934	traffic while still maintaining carrier on.
1936	9. SNMP agents
1937	===============
1939		If running SNMP agents, the bonding driver should be loaded
1940	before any network drivers participating in a bond.  This requirement
1941	is due to the interface index (ipAdEntIfIndex) being associated to
1942	the first interface found with a given IP address.  That is, there is
1943	only one ipAdEntIfIndex for each IP address.  For example, if eth0 and
1944	eth1 are slaves of bond0 and the driver for eth0 is loaded before the
1945	bonding driver, the interface for the IP address will be associated
1946	with the eth0 interface.  This configuration is shown below, the IP
1947	address has an interface index of 2 which indexes to eth0
1948	in the ifDescr table (ifDescr.2).
1950	     interfaces.ifTable.ifEntry.ifDescr.1 = lo
1951	     interfaces.ifTable.ifEntry.ifDescr.2 = eth0
1952	     interfaces.ifTable.ifEntry.ifDescr.3 = eth1
1953	     interfaces.ifTable.ifEntry.ifDescr.4 = eth2
1954	     interfaces.ifTable.ifEntry.ifDescr.5 = eth3
1955	     interfaces.ifTable.ifEntry.ifDescr.6 = bond0
1956	     ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex. = 5
1957	     ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex. = 2
1958	     ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex. = 4
1959	     ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex. = 1
1961		This problem is avoided by loading the bonding driver before
1962	any network drivers participating in a bond.  Below is an example of
1963	loading the bonding driver first, the IP address is
1964	correctly associated with ifDescr.2.
1966	     interfaces.ifTable.ifEntry.ifDescr.1 = lo
1967	     interfaces.ifTable.ifEntry.ifDescr.2 = bond0
1968	     interfaces.ifTable.ifEntry.ifDescr.3 = eth0
1969	     interfaces.ifTable.ifEntry.ifDescr.4 = eth1
1970	     interfaces.ifTable.ifEntry.ifDescr.5 = eth2
1971	     interfaces.ifTable.ifEntry.ifDescr.6 = eth3
1972	     ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex. = 6
1973	     ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex. = 2
1974	     ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex. = 5
1975	     ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex. = 1
1977		While some distributions may not report the interface name in
1978	ifDescr, the association between the IP address and IfIndex remains
1979	and SNMP functions such as Interface_Scan_Next will report that
1980	association.
1982	10. Promiscuous mode
1983	====================
1985		When running network monitoring tools, e.g., tcpdump, it is
1986	common to enable promiscuous mode on the device, so that all traffic
1987	is seen (instead of seeing only traffic destined for the local host).
1988	The bonding driver handles promiscuous mode changes to the bonding
1989	master device (e.g., bond0), and propagates the setting to the slave
1990	devices.
1992		For the balance-rr, balance-xor, broadcast, and 802.3ad modes,
1993	the promiscuous mode setting is propagated to all slaves.
1995		For the active-backup, balance-tlb and balance-alb modes, the
1996	promiscuous mode setting is propagated only to the active slave.
1998		For balance-tlb mode, the active slave is the slave currently
1999	receiving inbound traffic.
2001		For balance-alb mode, the active slave is the slave used as a
2002	"primary."  This slave is used for mode-specific control traffic, for
2003	sending to peers that are unassigned or if the load is unbalanced.
2005		For the active-backup, balance-tlb and balance-alb modes, when
2006	the active slave changes (e.g., due to a link failure), the
2007	promiscuous setting will be propagated to the new active slave.
2009	11. Configuring Bonding for High Availability
2010	=============================================
2012		High Availability refers to configurations that provide
2013	maximum network availability by having redundant or backup devices,
2014	links or switches between the host and the rest of the world.  The
2015	goal is to provide the maximum availability of network connectivity
2016	(i.e., the network always works), even though other configurations
2017	could provide higher throughput.
2019	11.1 High Availability in a Single Switch Topology
2020	--------------------------------------------------
2022		If two hosts (or a host and a single switch) are directly
2023	connected via multiple physical links, then there is no availability
2024	penalty to optimizing for maximum bandwidth.  In this case, there is
2025	only one switch (or peer), so if it fails, there is no alternative
2026	access to fail over to.  Additionally, the bonding load balance modes
2027	support link monitoring of their members, so if individual links fail,
2028	the load will be rebalanced across the remaining devices.
2030		See Section 12, "Configuring Bonding for Maximum Throughput"
2031	for information on configuring bonding with one peer device.
2033	11.2 High Availability in a Multiple Switch Topology
2034	----------------------------------------------------
2036		With multiple switches, the configuration of bonding and the
2037	network changes dramatically.  In multiple switch topologies, there is
2038	a trade off between network availability and usable bandwidth.
2040		Below is a sample network, configured to maximize the
2041	availability of the network:
2043	                |                                     |
2044	                |port3                           port3|
2045	          +-----+----+                          +-----+----+
2046	          |          |port2       ISL      port2|          |
2047	          | switch A +--------------------------+ switch B |
2048	          |          |                          |          |
2049	          +-----+----+                          +-----++---+
2050	                |port1                           port1|
2051	                |             +-------+               |
2052	                +-------------+ host1 +---------------+
2053	                         eth0 +-------+ eth1
2055		In this configuration, there is a link between the two
2056	switches (ISL, or inter switch link), and multiple ports connecting to
2057	the outside world ("port3" on each switch).  There is no technical
2058	reason that this could not be extended to a third switch.
2060	11.2.1 HA Bonding Mode Selection for Multiple Switch Topology
2061	-------------------------------------------------------------
2063		In a topology such as the example above, the active-backup and
2064	broadcast modes are the only useful bonding modes when optimizing for
2065	availability; the other modes require all links to terminate on the
2066	same peer for them to behave rationally.
2068	active-backup: This is generally the preferred mode, particularly if
2069		the switches have an ISL and play together well.  If the
2070		network configuration is such that one switch is specifically
2071		a backup switch (e.g., has lower capacity, higher cost, etc),
2072		then the primary option can be used to insure that the
2073		preferred link is always used when it is available.
2075	broadcast: This mode is really a special purpose mode, and is suitable
2076		only for very specific needs.  For example, if the two
2077		switches are not connected (no ISL), and the networks beyond
2078		them are totally independent.  In this case, if it is
2079		necessary for some specific one-way traffic to reach both
2080		independent networks, then the broadcast mode may be suitable.
2082	11.2.2 HA Link Monitoring Selection for Multiple Switch Topology
2083	----------------------------------------------------------------
2085		The choice of link monitoring ultimately depends upon your
2086	switch.  If the switch can reliably fail ports in response to other
2087	failures, then either the MII or ARP monitors should work.  For
2088	example, in the above example, if the "port3" link fails at the remote
2089	end, the MII monitor has no direct means to detect this.  The ARP
2090	monitor could be configured with a target at the remote end of port3,
2091	thus detecting that failure without switch support.
2093		In general, however, in a multiple switch topology, the ARP
2094	monitor can provide a higher level of reliability in detecting end to
2095	end connectivity failures (which may be caused by the failure of any
2096	individual component to pass traffic for any reason).  Additionally,
2097	the ARP monitor should be configured with multiple targets (at least
2098	one for each switch in the network).  This will insure that,
2099	regardless of which switch is active, the ARP monitor has a suitable
2100	target to query.
2102		Note, also, that of late many switches now support a functionality
2103	generally referred to as "trunk failover."  This is a feature of the
2104	switch that causes the link state of a particular switch port to be set
2105	down (or up) when the state of another switch port goes down (or up).
2106	Its purpose is to propagate link failures from logically "exterior" ports
2107	to the logically "interior" ports that bonding is able to monitor via
2108	miimon.  Availability and configuration for trunk failover varies by
2109	switch, but this can be a viable alternative to the ARP monitor when using
2110	suitable switches.
2112	12. Configuring Bonding for Maximum Throughput
2113	==============================================
2115	12.1 Maximizing Throughput in a Single Switch Topology
2116	------------------------------------------------------
2118		In a single switch configuration, the best method to maximize
2119	throughput depends upon the application and network environment.  The
2120	various load balancing modes each have strengths and weaknesses in
2121	different environments, as detailed below.
2123		For this discussion, we will break down the topologies into
2124	two categories.  Depending upon the destination of most traffic, we
2125	categorize them into either "gatewayed" or "local" configurations.
2127		In a gatewayed configuration, the "switch" is acting primarily
2128	as a router, and the majority of traffic passes through this router to
2129	other networks.  An example would be the following:
2132	     +----------+                     +----------+
2133	     |          |eth0            port1|          | to other networks
2134	     | Host A   +---------------------+ router   +------------------->
2135	     |          +---------------------+          | Hosts B and C are out
2136	     |          |eth1            port2|          | here somewhere
2137	     +----------+                     +----------+
2139		The router may be a dedicated router device, or another host
2140	acting as a gateway.  For our discussion, the important point is that
2141	the majority of traffic from Host A will pass through the router to
2142	some other network before reaching its final destination.
2144		In a gatewayed network configuration, although Host A may
2145	communicate with many other systems, all of its traffic will be sent
2146	and received via one other peer on the local network, the router.
2148		Note that the case of two systems connected directly via
2149	multiple physical links is, for purposes of configuring bonding, the
2150	same as a gatewayed configuration.  In that case, it happens that all
2151	traffic is destined for the "gateway" itself, not some other network
2152	beyond the gateway.
2154		In a local configuration, the "switch" is acting primarily as
2155	a switch, and the majority of traffic passes through this switch to
2156	reach other stations on the same network.  An example would be the
2157	following:
2159	    +----------+            +----------+       +--------+
2160	    |          |eth0   port1|          +-------+ Host B |
2161	    |  Host A  +------------+  switch  |port3  +--------+
2162	    |          +------------+          |                  +--------+
2163	    |          |eth1   port2|          +------------------+ Host C |
2164	    +----------+            +----------+port4             +--------+
2167		Again, the switch may be a dedicated switch device, or another
2168	host acting as a gateway.  For our discussion, the important point is
2169	that the majority of traffic from Host A is destined for other hosts
2170	on the same local network (Hosts B and C in the above example).
2172		In summary, in a gatewayed configuration, traffic to and from
2173	the bonded device will be to the same MAC level peer on the network
2174	(the gateway itself, i.e., the router), regardless of its final
2175	destination.  In a local configuration, traffic flows directly to and
2176	from the final destinations, thus, each destination (Host B, Host C)
2177	will be addressed directly by their individual MAC addresses.
2179		This distinction between a gatewayed and a local network
2180	configuration is important because many of the load balancing modes
2181	available use the MAC addresses of the local network source and
2182	destination to make load balancing decisions.  The behavior of each
2183	mode is described below.
2186	12.1.1 MT Bonding Mode Selection for Single Switch Topology
2187	-----------------------------------------------------------
2189		This configuration is the easiest to set up and to understand,
2190	although you will have to decide which bonding mode best suits your
2191	needs.  The trade offs for each mode are detailed below:
2193	balance-rr: This mode is the only mode that will permit a single
2194		TCP/IP connection to stripe traffic across multiple
2195		interfaces. It is therefore the only mode that will allow a
2196		single TCP/IP stream to utilize more than one interface's
2197		worth of throughput.  This comes at a cost, however: the
2198		striping generally results in peer systems receiving packets out
2199		of order, causing TCP/IP's congestion control system to kick
2200		in, often by retransmitting segments.
2202		It is possible to adjust TCP/IP's congestion limits by
2203		altering the net.ipv4.tcp_reordering sysctl parameter.  The
2204		usual default value is 3, and the maximum useful value is 127.
2205		For a four interface balance-rr bond, expect that a single
2206		TCP/IP stream will utilize no more than approximately 2.3
2207		interface's worth of throughput, even after adjusting
2208		tcp_reordering.
2210		Note that the fraction of packets that will be delivered out of
2211		order is highly variable, and is unlikely to be zero.  The level
2212		of reordering depends upon a variety of factors, including the
2213		networking interfaces, the switch, and the topology of the
2214		configuration.  Speaking in general terms, higher speed network
2215		cards produce more reordering (due to factors such as packet
2216		coalescing), and a "many to many" topology will reorder at a
2217		higher rate than a "many slow to one fast" configuration.
2219		Many switches do not support any modes that stripe traffic
2220		(instead choosing a port based upon IP or MAC level addresses);
2221		for those devices, traffic for a particular connection flowing
2222		through the switch to a balance-rr bond will not utilize greater
2223		than one interface's worth of bandwidth.
2225		If you are utilizing protocols other than TCP/IP, UDP for
2226		example, and your application can tolerate out of order
2227		delivery, then this mode can allow for single stream datagram
2228		performance that scales near linearly as interfaces are added
2229		to the bond.
2231		This mode requires the switch to have the appropriate ports
2232		configured for "etherchannel" or "trunking."
2234	active-backup: There is not much advantage in this network topology to
2235		the active-backup mode, as the inactive backup devices are all
2236		connected to the same peer as the primary.  In this case, a
2237		load balancing mode (with link monitoring) will provide the
2238		same level of network availability, but with increased
2239		available bandwidth.  On the plus side, active-backup mode
2240		does not require any configuration of the switch, so it may
2241		have value if the hardware available does not support any of
2242		the load balance modes.
2244	balance-xor: This mode will limit traffic such that packets destined
2245		for specific peers will always be sent over the same
2246		interface.  Since the destination is determined by the MAC
2247		addresses involved, this mode works best in a "local" network
2248		configuration (as described above), with destinations all on
2249		the same local network.  This mode is likely to be suboptimal
2250		if all your traffic is passed through a single router (i.e., a
2251		"gatewayed" network configuration, as described above).
2253		As with balance-rr, the switch ports need to be configured for
2254		"etherchannel" or "trunking."
2256	broadcast: Like active-backup, there is not much advantage to this
2257		mode in this type of network topology.
2259	802.3ad: This mode can be a good choice for this type of network
2260		topology.  The 802.3ad mode is an IEEE standard, so all peers
2261		that implement 802.3ad should interoperate well.  The 802.3ad
2262		protocol includes automatic configuration of the aggregates,
2263		so minimal manual configuration of the switch is needed
2264		(typically only to designate that some set of devices is
2265		available for 802.3ad).  The 802.3ad standard also mandates
2266		that frames be delivered in order (within certain limits), so
2267		in general single connections will not see misordering of
2268		packets.  The 802.3ad mode does have some drawbacks: the
2269		standard mandates that all devices in the aggregate operate at
2270		the same speed and duplex.  Also, as with all bonding load
2271		balance modes other than balance-rr, no single connection will
2272		be able to utilize more than a single interface's worth of
2273		bandwidth.  
2275		Additionally, the linux bonding 802.3ad implementation
2276		distributes traffic by peer (using an XOR of MAC addresses),
2277		so in a "gatewayed" configuration, all outgoing traffic will
2278		generally use the same device.  Incoming traffic may also end
2279		up on a single device, but that is dependent upon the
2280		balancing policy of the peer's 8023.ad implementation.  In a
2281		"local" configuration, traffic will be distributed across the
2282		devices in the bond.
2284		Finally, the 802.3ad mode mandates the use of the MII monitor,
2285		therefore, the ARP monitor is not available in this mode.
2287	balance-tlb: The balance-tlb mode balances outgoing traffic by peer.
2288		Since the balancing is done according to MAC address, in a
2289		"gatewayed" configuration (as described above), this mode will
2290		send all traffic across a single device.  However, in a
2291		"local" network configuration, this mode balances multiple
2292		local network peers across devices in a vaguely intelligent
2293		manner (not a simple XOR as in balance-xor or 802.3ad mode),
2294		so that mathematically unlucky MAC addresses (i.e., ones that
2295		XOR to the same value) will not all "bunch up" on a single
2296		interface.
2298		Unlike 802.3ad, interfaces may be of differing speeds, and no
2299		special switch configuration is required.  On the down side,
2300		in this mode all incoming traffic arrives over a single
2301		interface, this mode requires certain ethtool support in the
2302		network device driver of the slave interfaces, and the ARP
2303		monitor is not available.
2305	balance-alb: This mode is everything that balance-tlb is, and more.
2306		It has all of the features (and restrictions) of balance-tlb,
2307		and will also balance incoming traffic from local network
2308		peers (as described in the Bonding Module Options section,
2309		above).
2311		The only additional down side to this mode is that the network
2312		device driver must support changing the hardware address while
2313		the device is open.
2315	12.1.2 MT Link Monitoring for Single Switch Topology
2316	----------------------------------------------------
2318		The choice of link monitoring may largely depend upon which
2319	mode you choose to use.  The more advanced load balancing modes do not
2320	support the use of the ARP monitor, and are thus restricted to using
2321	the MII monitor (which does not provide as high a level of end to end
2322	assurance as the ARP monitor).
2324	12.2 Maximum Throughput in a Multiple Switch Topology
2325	-----------------------------------------------------
2327		Multiple switches may be utilized to optimize for throughput
2328	when they are configured in parallel as part of an isolated network
2329	between two or more systems, for example:
2331	                       +-----------+
2332	                       |  Host A   | 
2333	                       +-+---+---+-+
2334	                         |   |   |
2335	                +--------+   |   +---------+
2336	                |            |             |
2337	         +------+---+  +-----+----+  +-----+----+
2338	         | Switch A |  | Switch B |  | Switch C |
2339	         +------+---+  +-----+----+  +-----+----+
2340	                |            |             |
2341	                +--------+   |   +---------+
2342	                         |   |   |
2343	                       +-+---+---+-+
2344	                       |  Host B   | 
2345	                       +-----------+
2347		In this configuration, the switches are isolated from one
2348	another.  One reason to employ a topology such as this is for an
2349	isolated network with many hosts (a cluster configured for high
2350	performance, for example), using multiple smaller switches can be more
2351	cost effective than a single larger switch, e.g., on a network with 24
2352	hosts, three 24 port switches can be significantly less expensive than
2353	a single 72 port switch.
2355		If access beyond the network is required, an individual host
2356	can be equipped with an additional network device connected to an
2357	external network; this host then additionally acts as a gateway.
2359	12.2.1 MT Bonding Mode Selection for Multiple Switch Topology
2360	-------------------------------------------------------------
2362		In actual practice, the bonding mode typically employed in
2363	configurations of this type is balance-rr.  Historically, in this
2364	network configuration, the usual caveats about out of order packet
2365	delivery are mitigated by the use of network adapters that do not do
2366	any kind of packet coalescing (via the use of NAPI, or because the
2367	device itself does not generate interrupts until some number of
2368	packets has arrived).  When employed in this fashion, the balance-rr
2369	mode allows individual connections between two hosts to effectively
2370	utilize greater than one interface's bandwidth.
2372	12.2.2 MT Link Monitoring for Multiple Switch Topology
2373	------------------------------------------------------
2375		Again, in actual practice, the MII monitor is most often used
2376	in this configuration, as performance is given preference over
2377	availability.  The ARP monitor will function in this topology, but its
2378	advantages over the MII monitor are mitigated by the volume of probes
2379	needed as the number of systems involved grows (remember that each
2380	host in the network is configured with bonding).
2382	13. Switch Behavior Issues
2383	==========================
2385	13.1 Link Establishment and Failover Delays
2386	-------------------------------------------
2388		Some switches exhibit undesirable behavior with regard to the
2389	timing of link up and down reporting by the switch.
2391		First, when a link comes up, some switches may indicate that
2392	the link is up (carrier available), but not pass traffic over the
2393	interface for some period of time.  This delay is typically due to
2394	some type of autonegotiation or routing protocol, but may also occur
2395	during switch initialization (e.g., during recovery after a switch
2396	failure).  If you find this to be a problem, specify an appropriate
2397	value to the updelay bonding module option to delay the use of the
2398	relevant interface(s).
2400		Second, some switches may "bounce" the link state one or more
2401	times while a link is changing state.  This occurs most commonly while
2402	the switch is initializing.  Again, an appropriate updelay value may
2403	help.
2405		Note that when a bonding interface has no active links, the
2406	driver will immediately reuse the first link that goes up, even if the
2407	updelay parameter has been specified (the updelay is ignored in this
2408	case).  If there are slave interfaces waiting for the updelay timeout
2409	to expire, the interface that first went into that state will be
2410	immediately reused.  This reduces down time of the network if the
2411	value of updelay has been overestimated, and since this occurs only in
2412	cases with no connectivity, there is no additional penalty for
2413	ignoring the updelay.
2415		In addition to the concerns about switch timings, if your
2416	switches take a long time to go into backup mode, it may be desirable
2417	to not activate a backup interface immediately after a link goes down.
2418	Failover may be delayed via the downdelay bonding module option.
2420	13.2 Duplicated Incoming Packets
2421	--------------------------------
2423		NOTE: Starting with version 3.0.2, the bonding driver has logic to
2424	suppress duplicate packets, which should largely eliminate this problem.
2425	The following description is kept for reference.
2427		It is not uncommon to observe a short burst of duplicated
2428	traffic when the bonding device is first used, or after it has been
2429	idle for some period of time.  This is most easily observed by issuing
2430	a "ping" to some other host on the network, and noticing that the
2431	output from ping flags duplicates (typically one per slave).
2433		For example, on a bond in active-backup mode with five slaves
2434	all connected to one switch, the output may appear as follows:
2436	# ping -n
2437	PING ( from : 56(84) bytes of data.
2438	64 bytes from icmp_seq=1 ttl=64 time=13.7 ms
2439	64 bytes from icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2440	64 bytes from icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2441	64 bytes from icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2442	64 bytes from icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
2443	64 bytes from icmp_seq=2 ttl=64 time=0.216 ms
2444	64 bytes from icmp_seq=3 ttl=64 time=0.267 ms
2445	64 bytes from icmp_seq=4 ttl=64 time=0.222 ms
2447		This is not due to an error in the bonding driver, rather, it
2448	is a side effect of how many switches update their MAC forwarding
2449	tables.  Initially, the switch does not associate the MAC address in
2450	the packet with a particular switch port, and so it may send the
2451	traffic to all ports until its MAC forwarding table is updated.  Since
2452	the interfaces attached to the bond may occupy multiple ports on a
2453	single switch, when the switch (temporarily) floods the traffic to all
2454	ports, the bond device receives multiple copies of the same packet
2455	(one per slave device).
2457		The duplicated packet behavior is switch dependent, some
2458	switches exhibit this, and some do not.  On switches that display this
2459	behavior, it can be induced by clearing the MAC forwarding table (on
2460	most Cisco switches, the privileged command "clear mac address-table
2461	dynamic" will accomplish this).
2463	14. Hardware Specific Considerations
2464	====================================
2466		This section contains additional information for configuring
2467	bonding on specific hardware platforms, or for interfacing bonding
2468	with particular switches or other devices.
2470	14.1 IBM BladeCenter
2471	--------------------
2473		This applies to the JS20 and similar systems.
2475		On the JS20 blades, the bonding driver supports only
2476	balance-rr, active-backup, balance-tlb and balance-alb modes.  This is
2477	largely due to the network topology inside the BladeCenter, detailed
2478	below.
2480	JS20 network adapter information
2481	--------------------------------
2483		All JS20s come with two Broadcom Gigabit Ethernet ports
2484	integrated on the planar (that's "motherboard" in IBM-speak).  In the
2485	BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to
2486	I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2.
2487	An add-on Broadcom daughter card can be installed on a JS20 to provide
2488	two more Gigabit Ethernet ports.  These ports, eth2 and eth3, are
2489	wired to I/O Modules 3 and 4, respectively.
2491		Each I/O Module may contain either a switch or a passthrough
2492	module (which allows ports to be directly connected to an external
2493	switch).  Some bonding modes require a specific BladeCenter internal
2494	network topology in order to function; these are detailed below.
2496		Additional BladeCenter-specific networking information can be
2497	found in two IBM Redbooks (www.ibm.com/redbooks):
2499	"IBM eServer BladeCenter Networking Options"
2500	"IBM eServer BladeCenter Layer 2-7 Network Switching"
2502	BladeCenter networking configuration
2503	------------------------------------
2505		Because a BladeCenter can be configured in a very large number
2506	of ways, this discussion will be confined to describing basic
2507	configurations.
2509		Normally, Ethernet Switch Modules (ESMs) are used in I/O
2510	modules 1 and 2.  In this configuration, the eth0 and eth1 ports of a
2511	JS20 will be connected to different internal switches (in the
2512	respective I/O modules).
2514		A passthrough module (OPM or CPM, optical or copper,
2515	passthrough module) connects the I/O module directly to an external
2516	switch.  By using PMs in I/O module #1 and #2, the eth0 and eth1
2517	interfaces of a JS20 can be redirected to the outside world and
2518	connected to a common external switch.
2520		Depending upon the mix of ESMs and PMs, the network will
2521	appear to bonding as either a single switch topology (all PMs) or as a
2522	multiple switch topology (one or more ESMs, zero or more PMs).  It is
2523	also possible to connect ESMs together, resulting in a configuration
2524	much like the example in "High Availability in a Multiple Switch
2525	Topology," above.
2527	Requirements for specific modes
2528	-------------------------------
2530		The balance-rr mode requires the use of passthrough modules
2531	for devices in the bond, all connected to an common external switch.
2532	That switch must be configured for "etherchannel" or "trunking" on the
2533	appropriate ports, as is usual for balance-rr.
2535		The balance-alb and balance-tlb modes will function with
2536	either switch modules or passthrough modules (or a mix).  The only
2537	specific requirement for these modes is that all network interfaces
2538	must be able to reach all destinations for traffic sent over the
2539	bonding device (i.e., the network must converge at some point outside
2540	the BladeCenter).
2542		The active-backup mode has no additional requirements.
2544	Link monitoring issues
2545	----------------------
2547		When an Ethernet Switch Module is in place, only the ARP
2548	monitor will reliably detect link loss to an external switch.  This is
2549	nothing unusual, but examination of the BladeCenter cabinet would
2550	suggest that the "external" network ports are the ethernet ports for
2551	the system, when it fact there is a switch between these "external"
2552	ports and the devices on the JS20 system itself.  The MII monitor is
2553	only able to detect link failures between the ESM and the JS20 system.
2555		When a passthrough module is in place, the MII monitor does
2556	detect failures to the "external" port, which is then directly
2557	connected to the JS20 system.
2559	Other concerns
2560	--------------
2562		The Serial Over LAN (SoL) link is established over the primary
2563	ethernet (eth0) only, therefore, any loss of link to eth0 will result
2564	in losing your SoL connection.  It will not fail over with other
2565	network traffic, as the SoL system is beyond the control of the
2566	bonding driver.
2568		It may be desirable to disable spanning tree on the switch
2569	(either the internal Ethernet Switch Module, or an external switch) to
2570	avoid fail-over delay issues when using bonding.
2573	15. Frequently Asked Questions
2574	==============================
2576	1.  Is it SMP safe?
2578		Yes. The old 2.0.xx channel bonding patch was not SMP safe.
2579	The new driver was designed to be SMP safe from the start.
2581	2.  What type of cards will work with it?
2583		Any Ethernet type cards (you can even mix cards - a Intel
2584	EtherExpress PRO/100 and a 3com 3c905b, for example).  For most modes,
2585	devices need not be of the same speed.
2587		Starting with version 3.2.1, bonding also supports Infiniband
2588	slaves in active-backup mode.
2590	3.  How many bonding devices can I have?
2592		There is no limit.
2594	4.  How many slaves can a bonding device have?
2596		This is limited only by the number of network interfaces Linux
2597	supports and/or the number of network cards you can place in your
2598	system.
2600	5.  What happens when a slave link dies?
2602		If link monitoring is enabled, then the failing device will be
2603	disabled.  The active-backup mode will fail over to a backup link, and
2604	other modes will ignore the failed link.  The link will continue to be
2605	monitored, and should it recover, it will rejoin the bond (in whatever
2606	manner is appropriate for the mode). See the sections on High
2607	Availability and the documentation for each mode for additional
2608	information.
2610		Link monitoring can be enabled via either the miimon or
2611	arp_interval parameters (described in the module parameters section,
2612	above).  In general, miimon monitors the carrier state as sensed by
2613	the underlying network device, and the arp monitor (arp_interval)
2614	monitors connectivity to another host on the local network.
2616		If no link monitoring is configured, the bonding driver will
2617	be unable to detect link failures, and will assume that all links are
2618	always available.  This will likely result in lost packets, and a
2619	resulting degradation of performance.  The precise performance loss
2620	depends upon the bonding mode and network configuration.
2622	6.  Can bonding be used for High Availability?
2624		Yes.  See the section on High Availability for details.
2626	7.  Which switches/systems does it work with?
2628		The full answer to this depends upon the desired mode.
2630		In the basic balance modes (balance-rr and balance-xor), it
2631	works with any system that supports etherchannel (also called
2632	trunking).  Most managed switches currently available have such
2633	support, and many unmanaged switches as well.
2635		The advanced balance modes (balance-tlb and balance-alb) do
2636	not have special switch requirements, but do need device drivers that
2637	support specific features (described in the appropriate section under
2638	module parameters, above).
2640		In 802.3ad mode, it works with systems that support IEEE
2641	802.3ad Dynamic Link Aggregation.  Most managed and many unmanaged
2642	switches currently available support 802.3ad.
2644	        The active-backup mode should work with any Layer-II switch.
2646	8.  Where does a bonding device get its MAC address from?
2648		When using slave devices that have fixed MAC addresses, or when
2649	the fail_over_mac option is enabled, the bonding device's MAC address is
2650	the MAC address of the active slave.
2652		For other configurations, if not explicitly configured (with
2653	ifconfig or ip link), the MAC address of the bonding device is taken from
2654	its first slave device.  This MAC address is then passed to all following
2655	slaves and remains persistent (even if the first slave is removed) until
2656	the bonding device is brought down or reconfigured.
2658		If you wish to change the MAC address, you can set it with
2659	ifconfig or ip link:
2661	# ifconfig bond0 hw ether 00:11:22:33:44:55
2663	# ip link set bond0 address 66:77:88:99:aa:bb
2665		The MAC address can be also changed by bringing down/up the
2666	device and then changing its slaves (or their order):
2668	# ifconfig bond0 down ; modprobe -r bonding
2669	# ifconfig bond0 .... up
2670	# ifenslave bond0 eth...
2672		This method will automatically take the address from the next
2673	slave that is added.
2675		To restore your slaves' MAC addresses, you need to detach them
2676	from the bond (`ifenslave -d bond0 eth0'). The bonding driver will
2677	then restore the MAC addresses that the slaves had before they were
2678	enslaved.
2680	16. Resources and Links
2681	=======================
2683		The latest version of the bonding driver can be found in the latest
2684	version of the linux kernel, found on http://kernel.org
2686		The latest version of this document can be found in the latest kernel
2687	source (named Documentation/networking/bonding.txt).
2689		Discussions regarding the usage of the bonding driver take place on the
2690	bonding-devel mailing list, hosted at sourceforge.net. If you have questions or
2691	problems, post them to the list.  The list address is:
2693	bonding-devel@lists.sourceforge.net
2695		The administrative interface (to subscribe or unsubscribe) can
2696	be found at:
2698	https://lists.sourceforge.net/lists/listinfo/bonding-devel
2700		Discussions regarding the development of the bonding driver take place
2701	on the main Linux network mailing list, hosted at vger.kernel.org. The list
2702	address is:
2704	netdev@vger.kernel.org
2706		The administrative interface (to subscribe or unsubscribe) can
2707	be found at:
2709	http://vger.kernel.org/vger-lists.html#netdev
2711	Donald Becker's Ethernet Drivers and diag programs may be found at :
2712	 - http://web.archive.org/web/*/http://www.scyld.com/network/ 
2714	You will also find a lot of information regarding Ethernet, NWay, MII,
2715	etc. at www.scyld.com.
2717	-- END --
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