If you have a setup at OVH and think of setting up Vyatta/VyOS then you will need the following to get the setup up and running and routing traffic via the correct interface.

Based on the following tutorial by OVH http://help.ovh.co.uk/BridgeClient#link0 you will notice that you have to set the gateway and also manually set the route to go to eth0.

The Ubuntu equivalent is this:
post-up route add GATEWAY_VM dev eth0
To do the same in Vyatta/VyOS:
set protocols static interface-route GATEWAY_VM/32 next-hop-interface eth0