Wierd EIGRP routing issue

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Mar 13th, 2010
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Ive got an odd issue with EIGRP. I've got two sites with 3750's configured as distribution switched, each site also has a 3845 with a DS3 connecting them.

X.X.10.0/24 is configured on the site B distribution switch and show up correctly in the routing table of all 4 devices.

Everything was working fine until we rebooted switch B. Ever since the reboot, the routes are still on all devices as expected but when end points at site A try to ping X.X.10.40 and X.X.10.31 it times out and a trace route shows the site B router is sending it back to the site A router causing a loop. All other devices in the X.X.10.X/24 subnet are working properly.

When I do a show IP route X.X.10.40 or 10.30 on the site B router it only shows the /24 route pointing to the site B switch but that is not how it is actually routing the traffic. When I add static routes on the site B router to send traffic destined for the two individual hosts to the site B switch, it begins to work again. Any ideas what would cause this and how to fix it?

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Reza Sharifi Sat, 03/13/2010 - 15:35
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Check you config on switch-B and make sure it looks the same as before you reboot the switch. Hopefully you have back up of your configs to compare it with. Some times you make a config change and forget to save it (wr), when you reboot the switch it comes back with on older config the was not working.  That is problem with Cisco devices, as soon as you press the enter key the config take effect and if you forget to save when box  rebooted it can cause a lots of headache.



rcblack Sun, 03/14/2010 - 10:12
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The before and after configs are identical, that was the first thing I checked.


Jon Marshall Mon, 03/15/2010 - 14:03
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Problem is that there is not a lot of info.

Is router B still in the same state ie. it has routes to the switch B networks but it passes the traffic back to site A router ?

If so can you post "sh ip route" from router B and also post a traceroute from site A to one of the networks and then a traceroute one of the hosts in that network that you have a specific route setup for on router B.

Finally can you post router B running config as well.



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