EIGRP Unequal Cost Load Balancing

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Aug 31st, 2010
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I have a multipoint frame-relay network linking R1, R3 and R4.  I also have frame-relay point-to-points linking R1 and R4 and one linking R4 and R3.  I'm running EIGRP over the entire set up and am trying to do unequal cost load-balancing to make the multipoint network less preferred than the p2p's.  I reduced the bandwidth on the multipoint interfaces to 1024.  I haven't configured the variance yet because I noticed something strange and want to get to the bottom of it.  The routing tables of R1 and R3 still show the multipoing "leg" to each other.  The multipoint "leg" to R4 has been removed from the routing table.  Keep in mind, the variance is not yet configured.  Since EIGRP only uses the best route in the routing table, why are these multipoint "legs" still showing up?  I'm using an emulator running 12.4 on 3640's.

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kathpric Tue, 08/31/2010 - 13:38
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Hi Stephen,

Could you show us the output from the routing table and "show ip eigrp topology" for the prefix you're concerned with?  Which next hops are R1, R3, and R4?


bubbab1975 Tue, 08/31/2010 - 13:58
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Here's the text file for all 3 routers involved.

As you can see from the "sh ip eigrp top", the metric was changed on only one of the multipoint legs.  That doesn't make sense because I applied the bandwidth change to s0/0.134.  Both legs should show an increased metric thereby causing EIGRP to only display the point-to-point routes in the routing table.

On R3, the network is the EIGRP-learned network to focus on.

On R1, the network is the focus.  These are the point-to-points connected to R4.

s0/0.134 is the multipoint interface on all three routers

s0/0.104 is R1's p2p connection to s0/0.401 on R4

s0/0.304 is R3's p2p connection to s0/0.403 on R4

kathpric Tue, 08/31/2010 - 15:41
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Where exactly did you apply "bandwidth 1024"?  Was it on s0/0.134 on all R1, R3, and R4?  Or just on one of the routers?  If you look at "show ip eigrp topology" and "show ip eigrp topology" it will show you the minimum bandwidth for each path.


bubbab1975 Tue, 08/31/2010 - 15:43
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I applied a bandwidth of 1024 to the s0/0.134 interface on all 3 routers.

kathpric Tue, 08/31/2010 - 16:11
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From the information you've given, I would expect the metric to increase on all multipoint paths.  Could you send the output from "show ip eigrp topology" and "show ip eigrp topology" to give us a better idea of what values each path is using to get the metric?


bubbab1975 Tue, 08/31/2010 - 16:48
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Well, I had to erase my configs to do another excercise.  I went back and just did the frame-relay and eigrp to get the outputs you wanted but it works now.  I don't know if it was a problem with the simulator or something else but all is good now.  Thanks for taking the time to check it out.


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