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NAME
lagg — link aggregation and link failover interface
SYNOPSIS
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):
if_lagg_load="YES"
DESCRIPTION
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 default), lacp, loadbalance,
roundrobin, broadcast, and none. The protocols 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 net.link.lagg.failover_rx_all 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 Aggregation 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 converge 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 distribution if the hash is invalid or uses less of the
protocol header information. 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
net.link.lagg.default_use_flowid sysctl(8).
EXAMPLES
Create a link aggregation using LACP with two bge(4) Gigabit Ethernet interfaces:
# ifconfig bge0 up
# ifconfig bge1 up
# ifconfig lagg0 create
# ifconfig lagg0 laggproto lacp laggport bge0 laggport bge1 \
192.168.1.1 netmask 255.255.255.0
Create a link aggregation using ROUNDROBIN with two bge(4) Gigabit Ethernet 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 \
192.168.1.1 netmask 255.255.255.0
# 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 \
192.168.1.1 netmask 255.255.255.0
(Note the mac address of the wireless device is forced to match the wired device as a workaround.)
SEE ALSO
ng_one2many(4), ifconfig(8), sysctl(8)
HISTORY
The lagg device first appeared in FreeBSD 6.3.
AUTHORS
The lagg driver was written under the name trunk by Reyk Floeter <reyk@openbsd.org>. The LACP
implementation was written by YAMAMOTO Takashi for NetBSD.
BUGS
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.
Debian November 18, 2017 LAGG(4)