Failover Routing

[anthony.f]

Hi.

We have three sites configured in triangle fashion. We'll call them A,B,C. Site B has two routers and so do the other sites. EIGRP is set up. When I SHUT the serial connecting B and A, traffic gets rerouted to A through C. HOWEVER, when I shut the ETHERNET side of the router AT "B" connecting to "A," the traffic does NOT get rerouted through the second router to "C" Does Ethernet failure constitute a different response than serial during a failure? I will add configs if nec.

[rjackson · Accepted solution]

traffic from the networks behind the rtrs at B needs to be directed to the router that has a good ethernet. The problem is inside the lan not the wan. You might need hot standby routing protocol so the inside network will always use one router but fail over to the other when the primary dies.

[burgessjt]

Can this be done with DHCP? If not, got any suggestions on Ethernet failover?

[vcjones]

While it theoretically could be done with DHCP, the response time to failure would be minutes to hours. Assuming you have more than one router available on the Ethernet to provide outgoing access, the easiest solution in a Cisco environment is HSRP (look up the "standby ip" command for your IOS release on www.cisco.com. In a non-Cisco environment, your best bet is VRRP (Cisco is loath to license their HSRP patent). In a mixed environment, you're pretty much out of luck, as Cisco has avoided implementing VRRP except where forced by major customers, but you may be able to use "passive RIP" to get the job done if the clients are smart enough.

Good luck and have fun. There is a chapter on the topic in my book if you have a copy.

Vincent C Jones

www.networkingunlimited.com