Tech tip: Create separate routing table for multiple nics in Ubuntu

Scenario: 2 nics in Ubuntu machine, requirement to assign IPs from different VLANs to each of these interfaces, access from outside world to all the assigned IPs.

The situation was a bit complex since the machine was a VM in ESXi and each of these nics were added to portgroups of two VLANs 200 and 201. The first nic eth0 was assigned a gateway , and was accessible from outside world. The second nic eth1 was assigned IP in 201 VLAN, but was not able to ping to that machine from other machines in a different VLAN

Solution:

Inorder to solve the issue, we had to add an additional routing table, to select default route for packages which should go out of eth1. The following lines added to the eth1 interface configuration in /etc/networking/interfaces file did the trick

post-up ip route add default via 10.1111.0.1 dev eth1 table 101
post-up ip rule add from 10.111.0.0/25 lookup 101

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