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Forcing a route to leave a specific serial interface

slade
Level 1
Level 1

Hello I have a 3640 with two serial interfaces. Each is connected to a different ISP. One of those circuits is idle while the other is saturated during peak hours. I would like to force traffic leaving the router for a certain class C network out of the serial interface that has plenty of bandwidth. Can this be easily done?

Thanks

3 Replies 3

Erick Bergquist
Level 6
Level 6

You can use Policy based routing to force the one network over the other serial.

See http://www.cisco.com/warp/public/105/36.html

However, there is no guarantee return/inbound traffic to that network will come in on that serial interface. Are you using BGP or just static routes to the provider?

We are using BGP. Unfortunately it has never worked correctly and we are not sure how to fix it. The provider we struck the deal with is not sure either I am afraid... ugh. I tried just adding a static route like ip route x.x.x.x x.x.x.x serial1/0, and that did not change how traffic was being sent.

Thanks

As for the static route not forcing it out the other serial, perhaps the traffic is cached (fast switched or cef). clear the ip cache and see if that helps. Policy Based routing should also force it out that interface. Try the static route with the IP address as the next-hop and not the interface name.

Are you learning any BGP routes from the providers? If you can provide more details then perhaps we can offer some ideas.

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