Inequal routing tables

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Jul 14th, 2008
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Hi,


We have two core routers at our headquarters, and many of our remote sites have a link going to each router. I've noticed the CEF load-balancing isn't working very well. When I check the routing tables on both routers, I see they are inconsistent.


One core router shows both paths to a remote office; i.e., it's directly-connected T1 and it's neighbor router. But the other core router is only showing the directly-connected path. We are using EIGRP.


I can't figure out why the second router isn't showing both paths. Can someone offer some suggestions?


Thanks,

- Steve


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Richard Burts Mon, 07/14/2008 - 17:42
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Steve


Some details about your environment would be quite helpful. Perhaps you could post the interface configuration and router eigrp configuration from the routers? It also would be good to have the output of show ip topology for an example or two of the routes that do not behave as you expect.


HTH


Rick

rstevek Tue, 07/15/2008 - 09:13
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Hi Rick,


Thanks for the offer of help! I've narrowed down the problem somewhat, and I'll try to provide all of the relevant info.


So this is a hub-and-spoke network. There are two core routers at HQ, CoreA and CoreB. They are both patched into a Layer-3 switch named Gateway_Switch. Router VNH has a connection to each Core router.


The relevant interface & EIGRP configurations for each of these is in the attachment "configs.txt." The outputs of the "show ip eigrp topology 10.2.0.0/16" for the HQ routers and L3 switch are in "eigrp.txt."


I can see what the problem is - the route through Core-B has a metric 114 times lower than the route through Core-A, and my variance is only 3!


What I don't understand is why these other routers (such as 10.254.6.2) are advertising themselves as potential successors, and why the higher-hop-count path is then being advertised to Core-B.


One thing I'm unsure about is the role of auto-summary in all this. I've noticed it's inconsistant. In almost all our routers we are using auto-summary; in the VNH router we are using "no auto-summary."


Also, should we be using "network 10.0.0.0" in the EIGRP configuration in all routers?


Once upon a time, this was all working properly, and I'm not sure what changed.


Thanks!

- Steve




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