.\"	$OpenBSD: trunk.4,v 1.22 2008/01/06 13:46:47 jmc Exp $
.\"
.\" Copyright (c) 2005, 2006 Reyk Floeter <reyk@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: January 6 2008 $
.Dt TRUNK 4
.Os
.Sh NAME
.Nm trunk
.Nd link aggregation and link failover interface
.Sh SYNOPSIS
.Cd "pseudo-device trunk"
.Sh DESCRIPTION
The
.Nm
interface allows aggregation of multiple network interfaces as one virtual
.Nm
interface.
.Pp
A
.Nm
interface can be created using the
.Ic ifconfig trunk Ns Ar N Ic create
command.
It can use different link aggregation protocols specified
using the
.Ic trunkproto Ar proto
option.
Child interfaces can be added using the
.Ic trunkport Ar child-iface
option and removed using the
.Ic -trunkport Ar child-iface
option.
.Pp
The driver currently supports the trunk protocols
.Ic roundrobin
(the default),
.Ic failover ,
.Ic loadbalance ,
.Ic broadcast ,
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 roundrobin
Distributes outgoing traffic through all active ports
and accepts incoming traffic from any active port.
A round-robin scheduler is used to aggregate the traffic.
.It Ic failover
Sends and receives traffic only through the master 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.
.It Ic loadbalance
Distributes outgoing traffic through all active ports
and accepts incoming traffic from any active port.
A hash of the protocol header is used to maintain packet ordering.
The hash includes the Ethernet source and destination address, and, if
available, the VLAN tag, and the IP source and destination address.
.It Ic broadcast
Sends frames to all ports of the trunk and receives frames on any
port of the trunk.
.It Ic none
This protocol is intended to do nothing: it disables any traffic without
disabling the
.Nm
interface itself.
.El
.Pp
The configuration can be done at runtime or by setting up a
.Xr hostname.if 5
configuration file for
.Xr netstart 8 .
.Sh EXAMPLES
Create a simple round robin trunk with two bge(4) Gigabit Ethernet
interfaces:
.Bd -literal -offset indent
# ifconfig bge0 up
# ifconfig bge1 up
# ifconfig trunk0 trunkport bge0 trunkport bge1 \e
	192.168.1.1 netmask 255.255.255.0
.Ed
.Pp
The following example uses an active failover trunk 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 nwid my_net up
# ifconfig trunk0 trunkproto failover trunkport em0 trunkport ath0 \e
	192.168.1.1 netmask 255.255.255.0
.Ed
.Sh SEE ALSO
.Xr inet 4 ,
.Xr hostname.if 5 ,
.Xr ifconfig 8 ,
.Xr netstart 8
.Sh HISTORY
The
.Nm
device first appeared in
.Ox 3.8 .
.Sh AUTHORS
The
.Nm
driver was written by
.An Reyk Floeter Aq reyk@openbsd.org .
.Sh CAVEATS
The trunk protocols
.Ic roundrobin
and
.Ic loadbalance
require a switch which supports IEEE 802.3ad link aggregation
for multicast/broadcast packets.
Otherwise protocols which cannot properly deal with duplicate packets,
such as
.Xr inet6 4
duplicate address detection (DAD), will not work.