Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
LAGG(4)		       FreeBSD Kernel Interfaces Manual		       LAGG(4)

     lagg -- link aggregation and link failover	interface

     To	compile	this driver into the kernel, place the following line in your
     kernel configuration file:

	   device lagg

     Alternatively, to load the	driver as a module at boot time, place the
     following line in loader.conf(5):


     The lagg interface	allows aggregation of multiple network interfaces as
     one virtual lagg interface	for the	purpose	of providing fault-tolerance
     and high-speed links.

     A lagg interface can be created using the ifconfig	laggN create command.
     It	can use	different link aggregation protocols specified using the
     laggproto proto option.  Child interfaces can be added using the laggport
     child-iface option	and removed using the -laggport	child-iface option.

     The driver	currently supports the aggregation protocols failover (the de-
     fault), lacp, loadbalance,	roundrobin, broadcast, and none.  The proto-
     cols determine which ports	are used for outgoing traffic and whether a
     specific port accepts incoming traffic.  The interface link state is used
     to	validate if the	port is	active or not.

     failover	  Sends	traffic	only through the active	port.  If the master
		  port becomes unavailable, the	next active port is used.  The
		  first	interface added	is the master port; any	interfaces
		  added	after that are used as failover	devices.

		  By default, received traffic is only accepted	when they are
		  received through the active port.  This constraint can be
		  relaxed by setting the
		  sysctl(8) variable to	a nonzero value, which is useful for
		  certain bridged network setups.

     lacp	  Supports the IEEE 802.1AX (formerly 802.3ad) Link Aggrega-
		  tion Control Protocol	(LACP) and the Marker Protocol.	 LACP
		  will negotiate a set of aggregable links with	the peer in to
		  one or more Link Aggregated Groups.  Each LAG	is composed of
		  ports	of the same speed, set to full-duplex operation.  The
		  traffic will be balanced across the ports in the LAG with
		  the greatest total speed, in most cases there	will only be
		  one LAG which	contains all ports.  In	the event of changes
		  in physical connectivity, Link Aggregation will quickly con-
		  verge	to a new configuration.

     loadbalance  Balances outgoing traffic across the active ports based on
		  hashed protocol header information and accepts incoming
		  traffic from any active port.	 This is a static setup	and
		  does not negotiate aggregation with the peer or exchange
		  frames to monitor the	link.  The hash	includes the Ethernet
		  source and destination address, and, if available, the VLAN
		  tag, and the IP source and destination address.

     roundrobin	  Distributes outgoing traffic using a round-robin scheduler
		  through all active ports and accepts incoming	traffic	from
		  any active port.  Using roundrobin mode can cause unordered
		  packet arrival at the	client.	 Throughput might be limited
		  as the client	performs CPU-intensive packet reordering.

     broadcast	  Sends	frames to all ports of the LAG and receives frames on
		  any port of the LAG.

     none	  This protocol	is intended to do nothing: it disables any
		  traffic without disabling the	lagg interface itself.

     Each lagg interface is created at runtime using interface cloning.	 This
     is	most easily done with the ifconfig(8) create command or	using the
     cloned_interfaces variable	in rc.conf(5).

     The MTU of	the first interface to be added	is used	as the lagg MTU.  All
     additional	interfaces are required	to have	exactly	the same value.

     The loadbalance and lacp modes will use the RSS hash from the network
     card if available to avoid	computing one, this may	give poor traffic dis-
     tribution if the hash is invalid or uses less of the protocol header in-
     formation.	 Local hash computation	can be forced per interface by setting
     the -use_flowid ifconfig(8) flag.	The default for	new interfaces is set
     via the sysctl(8).

     Create a link aggregation using LACP with two bge(4) Gigabit Ethernet in-

	   # ifconfig bge0 up
	   # ifconfig bge1 up
	   # ifconfig lagg0 create
	   # ifconfig lagg0 laggproto lacp laggport bge0 laggport bge1 \ netmask

     Create a link aggregation using ROUNDROBIN	with two bge(4)	Gigabit	Ether-
     net interfaces and	set a stride of	500 packets per	interface:

	   # ifconfig bge0 up
	   # ifconfig bge1 up
	   # ifconfig lagg0 create
	   # ifconfig lagg0 laggproto roundrobin laggport bge0 laggport	bge1 \ netmask
	   # ifconfig lagg0 rr_limit 500

     The following example uses	an active failover interface to	set up roaming
     between wired and wireless	networks using two network devices.  Whenever
     the wired master interface	is unplugged, the wireless failover device
     will be used:

	   # ifconfig em0 up
	   # ifconfig ath0 ether 00:11:22:33:44:55
	   # ifconfig create wlan0 wlandev ath0	ssid my_net up
	   # ifconfig lagg0 create
	   # ifconfig lagg0 laggproto failover laggport	em0 laggport wlan0 \ netmask

     (Note the mac address of the wireless device is forced to match the wired
     device as a workaround.)

     The following example shows how to	create an infiniband failover inter-

	   # ifconfig ib0 up
	   # ifconfig ib1 up
	   # ifconfig lagg0 create laggtype infiniband
	   # ifconfig lagg0 laggproto failover laggport	ib0 laggport ib1 \ netmask

     ng_one2many(4), ifconfig(8), sysctl(8)

     The lagg device first appeared in FreeBSD 6.3.

     The lagg driver was written under the name	trunk by Reyk Floeter
     <>.  The LACP implementation was written by YAMAMOTO
     Takashi for NetBSD.

     There is no way to	configure LACP administrative variables, including
     system and	port priorities.  The current implementation always performs
     active-mode LACP and uses 0x8000 as system	and port priorities.

FreeBSD	13.0		       October 21, 2020			  FreeBSD 13.0


Want to link to this manual page? Use this URL:

home | help