I'm trying to solve specific problem regarding Docker containers and routing.
A Docker host is running several network interfaces (3G USB modems), each having internet access. So, in short;
eth0 - WAN IP 1
ppp0 - WAN IP 2
ppp1 - WAN IP 3
ppp2 - WAN IP 4
How to specify which NIC each container should use if I want container to use a specific one?
Yes I ahed very similar issue. Unfortunately I had to use VirtualBox for this to work properly.
I have used Vagrant to create VirtualBox Virtual Machine and provisioned it with Ansible and then changed default route of that VM. Something like this:
route add default gw IP2
That would mean creating 4 different VM's but thats how I would approach the problem.