I have an ISP billing system installed on Debian GNU/Linux 8, which has 3 NIC cards. The Server is connected to 3 Mikrotik routers. Each router is connected to different internet lines which means they have 3 different static public IP subnets.Currently the server is connected to router1 172.10.1.1/24 directly via eth0. the other two routers are reachable via the internet, but we have issue reaching them sometimes due to internet outage.This is the current network diagram: I have configured eth1 and eth2 and connected directly to the router2 and router3 respectivly using the following answers/guides:Is it possible to have multiple default gateways for outbound connections?https://www.thomas-krenn.com/en/wiki/Two_Default_Gateways_on_One_SystemI have configured them exactly according to the above links but I was not successful yet. All the 3 networks stopped communicating, even router1. I have been forced to rollback.What I would like to achieve is connecting all three routers directly to the Server so that they can communicate locally.
Debian Server with 3 NIC Communicating with 3 different IP subnets
routing;network interface;subnets