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ip load balancing over ethernet

roturner
Beginner
Beginner

If you have two wan routers each with a link to a remote network and a third router on the ethernet, the third router would have two equal cost routes to the remote router. Now if this third router is fast switching why when you look in the routing table do you see the two routes but no asterix against either. Also the router does per packet not per destination.

4 REPLIES 4

thisisshanky
Advisor
Advisor

I think, this would be seen only when you are using the show ip route command with the prefix paramater specified.

show ip route x.x.x.x.

where x.x.x.x is the remote network.

On the out put of above command, dont you see 2 route descriptor blocks, with an asterisk on the left side ?

Try forcing a load-sharing on the interface to per-destination, using ip load-sharing per-destination command.

Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus

Hi

No I dont see the asterix and this is part of my question as to why not? Also I think you are meaning ip load-sharing per-destination for CEF which we are not running. We do have ip route-cache so it should switch per destination. A sniffer reveals that it most certainly does not. I suspect a bug but one Cisco guy said on ethernet you do not get the asterix for equal cost routes and it is supposed to be documented on the CCO but I cannot find it and do not believe it either. If you could shed any light then it would be great. Thanks Roger

Um, it kinda sounds like you are not fast switching on that interface. Try to sho ip int and make sure that it is actually fast-switching. Also, do show interface switching (this is undocumented (TTBOMK)) and see if that helps. Also, assuming the box can take it, have you considered turning on CEF? It is much less evil than it used to be!

Just in case anyone reads this there is a bug in IOS with ATM on a 7200 series router whereby although set for either fast switching or CEF the router will only per packet load share.

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