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I have two networks, with one machine that is supposed to act as bridge between them. The bridge host is a Ubuntu 12.04 (64bit) connecting via OpenVPN to a remote network. The local network is 172.16.x.x, the remote one 192.168.y.y.

I have been able to configure the bridge, br0, to include eth0, but I cannot get it to include tun0 as well (neither from the command line with brctrl - error: can't add tun0 to bridge br0: Invalid argument - nor in /etc/network/interfaces). However, tun0 is the interface used by OpenVPN and therefore I reckon I need it. Also brctrl show doesn't even list tun0 even though I put it on the bridge_ports line in interfaces.

Now the OpenVPN connection obviously requires either eth0 to have a connection already, or br0 has to be up to establish the connection. This seems like a catch 22.

The idea is to configure routes for the 192.168.y.0/24 network to go through this bridge host. So I do not want to NAT here.

I'm flexible when it comes to using ebtables, iptables or whatever to facilitate this, but at the moment I am at a loss.

Okay strictly speaking I don't have to use bridging. But for routing I cannot see how that would bridge the gap between tun0 and eth0 ...

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