route output traffic from specific NAT'ed VM via ip alias

Question

In a dedicated server with several containers behind NAT, I'm trying to route the output / outbound traffic from one of the containers through a specific virtual interface attached to the main physical interface. Both interfaces have public IPs assigned to them.

The chain would look as follows:

OpenVZ container (10.10.10.2) > Host system (eth0:0; IP:1.2.3.4) > internet

as opposed to the current

OpenVZ container (10.10.10.2) > Host system (eth0; IP:5.6.7.8) > internet

I believe this can be done with an iptables postrouting rule

Answer 1

As it turned out, a simple postrouting rule did the trick.

iptables -t nat -A POSTROUTING -s '10.10.10.0/24' -o eth0 -j SNAT --to 1.2.3.4

I also had to delete a bunch of MASQUERADE postrouting rules that were just creating a big mess.