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Preferred route

Hi, I'm working on a configuration with our carrier and we have encountered an issue with equal costs routes. Our carrier has position two routers on our network. These routers serve as the gateway to our WAN. Router A has a 20mbps link, and Router B has a 5mbps link. Router A and B are configured with an HSRP address. When I assign the HSRP address to a PC, I see the expected "path" to the WAN. The path chosen is through Router A, the 20mbps link. Routers A and B are also redistributing its route table via EIGRP to a pair of internal routers (Routers C and D). I have a requirement to configure some PCs with Routers C and D as their gateway. In this configuration, these PCs do not always select Router A as the path to the WAN. Can someone suggest the best way to ensure the PC configured for Routers C and D, will always select the path through Router A as its preferred path. I guess I'm asking for a method to redistribute routes from Routers A and B to Routers C and D with some form of route costing.

Thank you.

1 REPLY

Re: Preferred route

Hi there,

The issue that you have is that the routes from routers A & B will have equal cost in EIGRP, so there is no real difference in the routers mind.

The best way to do this is with an offset-list. The router looks at the EIGRP metric, so you need to make one of the metrics worse than the other. Under the routing protocol you type something along the lines of:

"offset-list 1 (this is an access-list specifying the route you want) in #offset# f0/0"

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfeigrp.htm#wp1001049

OR - you could tell the router not to allow such a difference in the metrics on the first place by typing the command "max-paths 1" or "varience 1". This will make the router less tolerant of the other route. It will still have it in the database, but will not use it unless the other is unavailable.

Hope that helps,

LH

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