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.\" Copyright (c) 2005, 2006 Reyk Floeter <reyk@openbsd.org>
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.\" $FreeBSD: release/9.1.0/share/man/man4/lagg.4 236065 2012-05-26 08:21:11Z thompsa $
.\"
.Dd February 23, 2012
.Dt LAGG 4
.Os
.Sh NAME
.Nm lagg
.Nd link aggregation and link failover interface
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device lagg"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
if_lagg_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
interface allows aggregation of multiple network interfaces as one virtual
.Nm
interface for the purpose of providing fault-tolerance and high-speed links.
.Pp
A
.Nm
interface can be created using the
.Ic ifconfig lagg Ns Ar N Ic create
command.
It can use different link aggregation protocols specified
using the
.Ic laggproto Ar proto
option.
Child interfaces can be added using the
.Ic laggport Ar child-iface
option and removed using the
.Ic -laggport Ar child-iface
option.
.Pp
The driver currently supports the aggregation protocols
.Ic failover
(the default),
.Ic fec ,
.Ic lacp ,
.Ic loadbalance ,
.Ic roundrobin ,
and
.Ic 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.
.Bl -tag -width loadbalance
.It Ic 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.
.Pp
By default, received traffic is only accepted when they are received
through the active port.
This constraint can be relaxed by setting the
.Va net.link.lagg.failover_rx_all
.Xr sysctl 8
variable to a nonzero value,
which is useful for certain bridged network setups.
.It Ic fec
Supports Cisco EtherChannel.
This is an alias for
.Ic loadbalance
mode.
.It Ic lacp
Supports the IEEE 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.
.It Ic 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.
.It Ic roundrobin
Distributes outgoing traffic using a round-robin scheduler
through all active ports and accepts incoming traffic from
any active port.
.It Ic none
This protocol is intended to do nothing: it disables any traffic without
disabling the
.Nm
interface itself.
.El
.Pp
Each
.Nm
interface is created at runtime using interface cloning.
This is
most easily done with the
.Xr ifconfig 8
.Cm create
command or using the
.Va cloned_interfaces
variable in
.Xr rc.conf 5 .
.Pp
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.
.Pp
The
.Ic loadbalance
and
.Ic 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
.Va net.link.lagg.X.use_flowid
.Xr sysctl 8
variable to zero where X is the interface number.
The default for new interfaces is set via the
.Va net.link.lagg.default_use_flowid
.Xr sysctl 8 .
.Sh EXAMPLES
Create a 802.3ad link aggregation using LACP with two
.Xr bge 4
Gigabit Ethernet interfaces:
.Bd -literal -offset indent
# ifconfig bge0 up
# ifconfig bge1 up
# ifconfig lagg0 laggproto lacp laggport bge0 laggport bge1 \e
	192.168.1.1 netmask 255.255.255.0
.Ed
.Pp
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:
.Bd -literal -offset indent
# ifconfig em0 up
# ifconfig ath0 ether 00:11:22:33:44:55
# ifconfig create wlan0 wlandev ath0 ssid my_net up
# ifconfig lagg0 laggproto failover laggport em0 laggport wlan0 \e
	192.168.1.1 netmask 255.255.255.0
.Ed
.Pp
(Note the mac address of the wireless device is forced to match the wired
device as a workaround.)
.Sh SEE ALSO
.Xr ng_fec 4 ,
.Xr ng_one2many 4 ,
.Xr sysctl 8 ,
.Xr ifconfig 8
.Sh HISTORY
The
.Nm
device first appeared in
.Fx 6.3 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written under the name
.Nm trunk
by
.An Reyk Floeter Aq reyk@openbsd.org .
The LACP implementation was written by
.An YAMAMOTO Takashi
for
.Nx .
.Sh 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.