This scripts and config for /etc/network/interfaces allows to use internet from 2 providers simultaneously. Server is avaliable outside from both addresses. Script is used to switch default route if it fails.
I've often seen such setups, each time reinventing the wheel. So I decided to write and share some more common solution for Debian/Ubuntu systems. May be adopted for CentOS/RedHat.
- If default provider fails, and it's interface is still alive, default route is switched to other provider.
- Minimal configuration: you should not write ip addrsses to 100500 places in different scripts, all network parameters are taken from interfaces
- Conection is checked with ICMP ping to 2 ip addresses, but you can easy add something else to function
get_status(). - Server is avaliable outside from both IP addresses. Necessary tables and rules for policy-based routing are created.
- Scripts are mistake-proofing: you may use ifup/ifdown mixed with manual interface configuration, routing tables won't be broken.
- State file with name of currently used default interface.
- Log file. Both links are monitored, even if only one is used as default.
- Work with 2 providers on 1 interfaces with aliases:
eth0:0eth0:1 - Work with default route with load balancing - smth. like
nexthop via $IP1 dev $IFACE1 weight 1 nexthop via $IP2 dev $IFACE2 weight 1
P.S. If this code is useful for you - don't forget to put a star on it's github repo.