Automatic switch wifi/ethernet on OpenBSD

Author: Solène

Date: 30 August 2018

Tags: openbsd70 openbsd networking highlight

NILToday I will cover a specific topic on OpenBSD networking. If you are using a

laptop, you may switch from ethernet to wireless network from time to time.

There is a simple way to keep the network instead of having to disconnect /

reconnect everytime.

It's possible to aggregate your wireless and ethernet devices into one trunk

pseudo device in failover mode, which give ethernet the priority if connected.

To achieve this, it's quite simple. If you have devices **em0** and **iwm0**

create the following files.

**/etc/hostname.em0**

up

**/etc/hostname.iwm0**

join "office_network" wpakey "mypassword"

join "my_home_network" wpakey "9charshere"

join "roaming phone" wpakey "something"

join "Public Wifi"

up

**/etc/hostname.trunk0**

trunkproto failover trunkport em0 trunkport iwm0

autoconf

As you can see in the wireless device configuration we can specify multiples

network to join, it is a new feature that will be available from 6.4 release.

You can enable the new configuration by running `sh /etc/netstart` as root.

This setup is explained in [trunk(4)](http://man.openbsd.org/trunk.4)

man page and in the

[OpenBSD FAQ](https://www.openbsd.org/faq/faq6.html#Wireless) as well.