Error RTNETLINK answers: File exists
The problem was that two default gateways were being set, one static and one by dhcp. You can't have two default gateways with the same metric.
https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/1043244/comments/8
The solution: remove the gateway line from the configuration of eth1.
Or, add an explicit metric 100 line to eth1, to give the eth1 gateway a lower priority than the eth2 gateway.