Trunk failover setup on OpenBSD
I have a dedicated machine at home that I use mainly for sending and receiving e-mails. The machine has one wired interface as well as a wireless interface. My wired interface goes over a powerline adapter. For various reasons every once in a while, the powerline adapter loses sync and as a result I cannot access my machine remotely. One way to solve this problem is to take advantage of the wireless interface and transparently switch over to it whenever the wired interface becomes unavailable. To do this we’ll use a simple form of interface aggregation, also known as trunk failover. For the gory details please refer to:
# man 4 trunk
Setting up the interfaces
nwid <ESSID> wpakey <your-key> chan <your-channel> up
trunkproto failover trunkport alc0 trunkport athn0 inet 192.168.1.2 255.255.255.0 NONE media 100baseTX mediaopt full-duplex
Setting up the wired and wireless interfaces is straightforward and not
Our trunk setup is using the failover mode and is specified via
We have two allocated ports, the master port is hooked up to the wired interface
and the failover port is attached to the wireless interface.
In my setup I use a static IP address for the trunk interface but it is also
possible to use DHCP.
At this point restart the interfaces:
# sh /etc/netstart
Testing the trunk interface
Generate some network activity by copying a large file via scp and pull the ethernet cable from your machine. The copy operation might stall but it will automatically switch over to the wireless interface. If you plug your ethernet cable back in it will switch to the wired interface.
A sample ifconfig follows from my particular setup:
trunk0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 lladdr 90:e6:ba:74:0e:38 priority: 0 trunk: trunkproto failover trunkport athn0 trunkport alc0 master,active groups: trunk egress media: Ethernet autoselect status: active inet 192.168.1.2 netmask 0xffffff00 broadcast 192.168.1.255 inet6 fe80::92e6:baff:fe74:e38%trunk0 prefixlen 64 scopeid 0x5
That’s all :)