Backup FR Sub-Interface - Static Routing - Possible?

[rmarshall]

Lets assume two frame relay t1's coming into a router, the intent being that if one t1 fails the other will carry the load. Say it's a 1720 with two WIC's. S0 connects to the frame cloud, S0.1 has a PVC with DLCI 16 which points to the upstram neighbor using the IP of E0.
S1 connects to the frame cloud, S1.1 has a PVC with DLCI 16 which also points to the upstream neighbor using the IP of E0.

There is a default route of

IP route 0.0.0.0 0.0.0.0 S0.1

Assuming that S1.1 is configured as a backup for s0.1, how do I change the route so that 0.0.0.0 0.0.0.0 now points to s1.1?

Also, on the upstream router, 172.16.1.0 255.255.255.0 points down the pipe to the PVC with S0.1 on the downstream, how do I get that to switch to go down the PVC that points to S1.1 Is it time for me to move away from static routes?

 

[ewiley]

Program a default route the same way for s1.1, except make the metric larger. That way, when s0 goes down, the route through s1.1 will be selected (since the router removes all refrences to a down interface from the routing table, including default routes).

remote(config)# ip route 0.0.0.0 0.0.0.0 s1.1 5

since the metric of 5 is higher than the default metric of static routes (1, i believe) it will only be used when the other default route is gone

You also have to also add a route to the upstream router to your eth0 ip range through s1.1, again, making the metric higher.

upstream(config)# ip route <eth_ip's> <eth_mask> <backup_serial_interface> 5

This will not load-balance, but it will creat a fail-over situation if need-be. If you want load-balancing, just run ospf or eigrp between the 2 routers and you should be fine (i believe eigrp automatically load-balances over 4 links, and can be configured for up to 6).

Hope this helps!