[SOLVED] Route Setup

jstephens84 · 03-20-2015, 09:36 AM

So I have run into a weird setup that I could use help. I have a linux server with eth0 having 192.168.12.2 plugged into lan 1 on a switch with IP of 192.168.12.1. eth1 is 192.168.13.2 plugged into switch port 2 with IP of 192.168.13.1 . This is a layer 3 switch. I then have two other vlans 192.168.14.x and 192.168.15.x with servers on each.

The goal is to make it so that I can consolidate mail servers into one server and not have to reconfigure 230 linux servers to point to a single ip. They can continue to use the old server ip's that they were using before. Phase 1 upgrade the OS. Phase 2 touch all servers and send them to a single IP and remove the need for two ip address on the mail server.

The problem is that I have a default gateway for all traffic going to eth1. So when one of my servers attempts to get mail on 192.168.12.2 the traffic goes out eth1 instead of going out eht0 which is where the traffic came in on. If I remove the default traffic neither communication stops. the big problem is that the servers can reach both IP's on the mail servers.

Any help this you could give would be helpful.

jstephens84 · 03-20-2015, 10:15 AM

Ok I have found the solution. First make sure you have iproute2 or iproute installed. (I was using Scientific Linux 6.5 and it was already there). Then I did the following

Code:

echo "1 test" >> /etc/iproute2/rt_tables
ip route add 192.168.13.0/24 dev eth1 src 192.168.13.2 table test
ip route add default via 192.168.13.1 dev eth1 table test

ip rule add from 192.168.13.0/24 table test
ip rule add to 192.168.13.0/24 table test

ip route flush cache

basically you are creating routing policies. I hope this helps someone else having this issue.