NAME
trunk
—
link aggregation and link failover
interface
SYNOPSIS
pseudo-device trunk
DESCRIPTION
The trunk
interface allows aggregation of
multiple network interfaces as one virtual trunk
interface.
A trunk
interface can be created using the
ifconfig trunk
N
create
command. It can use different link
aggregation protocols specified using the trunkproto
proto option. Child interfaces can be added using the
trunkport
child-iface option
and removed using the -trunkport
child-iface option.
The driver currently supports the trunk protocols
broadcast
, failover
,
lacp
, loadbalance
,
none
, and roundrobin
(the
default). 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.
broadcast
- Sends frames to all ports of the trunk and receives frames on any port of the trunk.
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.
lacp
- Uses the IEEE 802.3ad Link Aggregation Control Protocol (LACP) and the Marker Protocol to increase link speed and provide redundancy. LACP trunk groups are composed of ports of the same speed, set to full-duplex operation. This protocol requires a switch which supports LACP.
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.
none
- This protocol is intended to do nothing: it disables any traffic without
disabling the
trunk
interface itself. 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.
The configuration can be done at runtime or by setting up a hostname.if(5) configuration file for netstart(8).
EXAMPLES
Create a simple round robin trunk with two bge(4) Gigabit Ethernet interfaces:
# ifconfig bge0 up # ifconfig bge1 up # ifconfig trunk0 trunkport bge0 trunkport bge1 \ 192.168.1.1 netmask 255.255.255.0
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:
# ifconfig em0 up # ifconfig ath0 nwid my_net up # ifconfig trunk0 trunkproto failover trunkport em0 trunkport ath0 \ 192.168.1.1 netmask 255.255.255.0
SEE ALSO
HISTORY
The trunk
device first appeared in
OpenBSD 3.8.
AUTHORS
The trunk
driver was written by
Reyk Floeter
<reyk@openbsd.org>.
CAVEATS
The trunk protocols loadbalance
and
roundrobin
require a switch which supports IEEE
802.3ad static link aggregation; otherwise protocols such as
inet6(4) duplicate address detection (DAD) cannot properly deal with
duplicate packets.
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.
The trunk
interface takes its MTU from the
first trunkport
. To avoid mismatches, adding a child
interface with a different MTU is not permitted.