Dual gateways

joel112 · 04-05-2006, 03:51 AM

basically our setup is as follows:

Code:

                              internet
                                  |
                                  |
                              LinuxRouter
                                  |
                                  |
                        __________|__________        
Subnet 192.168.1.0/24  |                     |
                    Router1               Router2
                       |                     |
                       |                     |
                       |_____________________|
                                  |
                                  |
                     Workstation Subnet 192.168.2.0/24

Router 1 and 2 route from the workstation subnet out to the LinuxRouter fine, and all the traffic comes back via router1, as thats the default gateway for the linuxrouter interface on that subnet.

There are 2 different gateways set on the LinuxRouter, router1(192.168.1.100, metric 1) and router2(192.168.1.102, metric 2). When router1 (The default) goes down, the LinuxRouter is no longer able to route packets to the workstation subnet. Is there a way to detect that either of the gateways has gone down, to switch to the other? Via a script/program of somesorts?

Joel

acid_kewpie · 04-05-2006, 07:20 AM

there are plenty of ways to configure gateway failovers and such, i'd suggest looking at some docs at lartc.org for details of configuring these more advanced routing scenarios.the alternative angle you may want to look at is resilience within the routers themselves, and have a floating address fail over between the two boxes in the event of a failured. for this form of resilience, check linux-ha.org for details of heartbeat monitoring and such.

baldy3105 · 04-06-2006, 09:53 AM

You want to implement VRRP on both sides of your routers. VRRP allows the two interfaces on a subnet to hide behind one virtual MAC / IP pair. One acts as primary the other as backup. If the primary goes down the backup simply starts routing instead. Implement this on both sides of your routers and you have a fully redundant pair.