bonding.txt

linux 内核源代码

	The default is slow.

max_bonds

	Specifies the number of bonding devices to create for this
	instance of the bonding driver.  E.g., if max_bonds is 3, and
	the bonding driver is not already loaded, then bond0, bond1
	and bond2 will be created.  The default value is 1.

miimon

	Specifies the MII link monitoring frequency in milliseconds.
	This determines how often the link state of each slave is
	inspected for link failures.  A value of zero disables MII
	link monitoring.  A value of 100 is a good starting point.
	The use_carrier option, below, affects how the link state is
	determined.  See the High Availability section for additional
	information.  The default value is 0.

mode

	Specifies one of the bonding policies. The default is
	balance-rr (round robin).  Possible values are:

	balance-rr or 0

		Round-robin policy: Transmit packets in sequential
		order from the first available slave through the
		last.  This mode provides load balancing and fault
		tolerance.

	active-backup or 1

		Active-backup policy: Only one slave in the bond is
		active.  A different slave becomes active if, and only
		if, the active slave fails.  The bond's MAC address is
		externally visible on only one port (network adapter)
		to avoid confusing the switch.

		In bonding version 2.6.2 or later, when a failover
		occurs in active-backup mode, bonding will issue one
		or more gratuitous ARPs on the newly active slave.
		One gratuitous ARP is issued for the bonding master
		interface and each VLAN interfaces configured above
		it, provided that the interface has at least one IP
		address configured.  Gratuitous ARPs issued for VLAN
		interfaces are tagged with the appropriate VLAN id.

		This mode provides fault tolerance.  The primary
		option, documented below, affects the behavior of this
		mode.

	balance-xor or 2

		XOR policy: Transmit based on the selected transmit
		hash policy.  The default policy is a simple [(source
		MAC address XOR'd with destination MAC address) modulo
		slave count].  Alternate transmit policies may be
		selected via the xmit_hash_policy option, described
		below.

		This mode provides load balancing and fault tolerance.

	broadcast or 3

		Broadcast policy: transmits everything on all slave
		interfaces.  This mode provides fault tolerance.

	802.3ad or 4

		IEEE 802.3ad Dynamic link aggregation.  Creates
		aggregation groups that share the same speed and
		duplex settings.  Utilizes all slaves in the active
		aggregator according to the 802.3ad specification.

		Slave selection for outgoing traffic is done according
		to the transmit hash policy, which may be changed from
		the default simple XOR policy via the xmit_hash_policy
		option, documented below.  Note that not all transmit
		policies may be 802.3ad compliant, particularly in
		regards to the packet mis-ordering requirements of
		section 43.2.4 of the 802.3ad standard.  Differing
		peer implementations will have varying tolerances for
		noncompliance.

		Prerequisites:

		1. Ethtool support in the base drivers for retrieving
		the speed and duplex of each slave.

		2. A switch that supports IEEE 802.3ad Dynamic link
		aggregation.

		Most switches will require some type of configuration
		to enable 802.3ad mode.

	balance-tlb or 5

		Adaptive transmit load balancing: channel bonding that
		does not require any special switch support.  The
		outgoing traffic is distributed according to the
		current load (computed relative to the speed) on each
		slave.  Incoming traffic is received by the current
		slave.  If the receiving slave fails, another slave
		takes over the MAC address of the failed receiving
		slave.

		Prerequisite:

		Ethtool support in the base drivers for retrieving the
		speed of each slave.

	balance-alb or 6

		Adaptive load balancing: includes balance-tlb plus
		receive load balancing (rlb) for IPV4 traffic, and
		does not require any special switch support.  The
		receive load balancing is achieved by ARP negotiation.
		The bonding driver intercepts the ARP Replies sent by
		the local system on their way out and overwrites the
		source hardware address with the unique hardware
		address of one of the slaves in the bond such that
		different peers use different hardware addresses for
		the server.

		Receive traffic from connections created by the server
		is also balanced.  When the local system sends an ARP
		Request the bonding driver copies and saves the peer's
		IP information from the ARP packet.  When the ARP
		Reply arrives from the peer, its hardware address is
		retrieved and the bonding driver initiates an ARP
		reply to this peer assigning it to one of the slaves
		in the bond.  A problematic outcome of using ARP
		negotiation for balancing is that each time that an
		ARP request is broadcast it uses the hardware address
		of the bond.  Hence, peers learn the hardware address
		of the bond and the balancing of receive traffic
		collapses to the current slave.  This is handled by
		sending updates (ARP Replies) to all the peers with
		their individually assigned hardware address such that
		the traffic is redistributed.  Receive traffic is also
		redistributed when a new slave is added to the bond
		and when an inactive slave is re-activated.  The
		receive load is distributed sequentially (round robin)
		among the group of highest speed slaves in the bond.

		When a link is reconnected or a new slave joins the
		bond the receive traffic is redistributed among all
		active slaves in the bond by initiating ARP Replies
		with the selected MAC address to each of the
		clients. The updelay parameter (detailed below) must
		be set to a value equal or greater than the switch's
		forwarding delay so that the ARP Replies sent to the
		peers will not be blocked by the switch.

		Prerequisites:

		1. Ethtool support in the base drivers for retrieving
		the speed of each slave.

		2. Base driver support for setting the hardware
		address of a device while it is open.  This is
		required so that there will always be one slave in the
		team using the bond hardware address (the
		curr_active_slave) while having a unique hardware
		address for each slave in the bond.  If the
		curr_active_slave fails its hardware address is
		swapped with the new curr_active_slave that was
		chosen.

primary

	A string (eth0, eth2, etc) specifying which slave is the
	primary device.  The specified device will always be the
	active slave while it is available.  Only when the primary is
	off-line will alternate devices be used.  This is useful when
	one slave is preferred over another, e.g., when one slave has
	higher throughput than another.

	The primary option is only valid for active-backup mode.

updelay

	Specifies the time, in milliseconds, to wait before enabling a
	slave after a link recovery has been detected.  This option is
	only valid for the miimon link monitor.  The updelay value
	should be a multiple of the miimon value; if not, it will be
	rounded down to the nearest multiple.  The default value is 0.

use_carrier

	Specifies whether or not miimon should use MII or ETHTOOL
	ioctls vs. netif_carrier_ok() to determine the link
	status. The MII or ETHTOOL ioctls are less efficient and
	utilize a deprecated calling sequence within the kernel.  The
	netif_carrier_ok() relies on the device driver to maintain its
	state with netif_carrier_on/off; at this writing, most, but
	not all, device drivers support this facility.

	If bonding insists that the link is up when it should not be,
	it may be that your network device driver does not support
	netif_carrier_on/off.  The default state for netif_carrier is
	"carrier on," so if a driver does not support netif_carrier,
	it will appear as if the link is always up.  In this case,
	setting use_carrier to 0 will cause bonding to revert to the
	MII / ETHTOOL ioctl method to determine the link state.

	A value of 1 enables the use of netif_carrier_ok(), a value of
	0 will use the deprecated MII / ETHTOOL ioctls.  The default
	value is 1.

xmit_hash_policy

	Selects the transmit hash policy to use for slave selection in
	balance-xor and 802.3ad modes.  Possible values are:

	layer2

		Uses XOR of hardware MAC addresses to generate the
		hash.  The formula is

		(source MAC XOR destination MAC) modulo slave count

		This algorithm will place all traffic to a particular
		network peer on the same slave.

		This algorithm is 802.3ad compliant.

	layer2+3

		This policy uses a combination of layer2 and layer3
		protocol information to generate the hash.

		Uses XOR of hardware MAC addresses and IP addresses to
		generate the hash.  The formula is

		(((source IP XOR dest IP) AND 0xffff) XOR
			( source MAC XOR destination MAC ))
				modulo slave count

		This algorithm will place all traffic to a particular
		network peer on the same slave.  For non-IP traffic,
		the formula is the same as for the layer2 transmit
		hash policy.

		This policy is intended to provide a more balanced
		distribution of traffic than layer2 alone, especially
		in environments where a layer3 gateway device is
		required to reach most destinations.

		This algorithm is 802.3ad complient.

	layer3+4

		This policy uses upper layer protocol information,
		when available, to generate the hash.  This allows for
		traffic to a particular network peer to span multiple
		slaves, although a single connection will not span
		multiple slaves.

		The formula for unfragmented TCP and UDP packets is

		((source port XOR dest port) XOR
			 ((source IP XOR dest IP) AND 0xffff)
				modulo slave count

		For fragmented TCP or UDP packets and all other IP
		protocol traffic, the source and destination port
		information is omitted.  For non-IP traffic, the
		formula is the same as for the layer2 transmit hash
		policy.

		This policy is intended to mimic the behavior of
		certain switches, notably Cisco switches with PFC2 as
		well as some Foundry and IBM products.

		This algorithm is not fully 802.3ad compliant.  A
		single TCP or UDP conversation containing both
		fragmented and unfragmented packets will see packets
		striped across two interfaces.  This may result in out
		of order delivery.  Most traffic types will not meet
		this criteria, as TCP rarely fragments traffic, and
		most UDP traffic is not involved in extended
		conversations.  Other implementations of 802.3ad may
		or may not tolerate this noncompliance.

	The default value is layer2.  This option was added in bonding
	version 2.6.3.  In earlier versions of bonding, this parameter
	does not exist, and the layer2 policy is the only policy.  The
	layer2+3 value was added for bonding version 3.2.2.


3. Configuring Bonding Devices
==============================

	You can configure bonding using either your distro's network
initialization scripts, or manually using either ifenslave or the
sysfs interface.  Distros generally use one of two packages for the
network initialization scripts: initscripts or sysconfig.  Recent
versions of these packages have support for bonding, while older
versions do not.

	We will first describe the options for configuring bonding for
distros using versions of initscripts and sysconfig with full or
partial support for bonding, then provide information on enabling
bonding without support from the network initialization scripts (i.e.,
older versions of initscripts or sysconfig).

	If you're unsure whether your distro uses sysconfig or
initscripts, or don't know if it's new enough, have no fear.
Determining this is fairly straightforward.

	First, issue the command:

$ rpm -qf /sbin/ifup

	It will respond with a line of text starting with either
"initscripts" or "sysconfig," followed by some numbers.  This is the
package that provides your network initialization scripts.

	Next, to determine if your installation supports bonding,
issue the command:

$ grep ifenslave /sbin/ifup

	If this returns any matches, then your initscripts or
sysconfig has support for bonding.