Strange issue with Multicast and EIGRP on a 2801

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Mar 6th, 2008
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Ran into this the other day. A 2801 router running IP Base 128M ram. Running EIGRP routing protocol. When we enabled multicast routing and IP pim sparse-dense-mode on the interfaces, within 5 minutes the telnet connection drops and we are unable to ping the router except from the directly connected interface, and cannot telnet into the router at all. Eventually we will get eigrp timeouts and resets, and then no longer able to ping the router. When we remove multicast, routing returns to normal. We changed the IOS to SPSERVICES of a known good image that we run on other routers just fine. Searching the Cisco site came up empty. There are no logs or anything to look at, and CPU/Memory was OK. We dont have access to the console unless we dispatch someone out, so troubleshooting this has become a pain. Any Ideas where to go from here? Can this be a hardware issue? Only card installed is a WIC-1DSU-T1-V2 card.

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Mohamed Sobair Thu, 03/06/2008 - 13:20
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What do u mean by eigrp timed out and rest? and what ip sparse-dense has to do with eigrp ?

If you mean Eigrp packets and Multicast packet, then this is not in concern.

The multicast Hellos used by a routing protocol are reserved range ( and has link local validity.

The sparse-dense multicast uses & to announce the RP in dense mode. which is totall different multicast range.

Propaply you have another issue,



tahequivoice Thu, 03/06/2008 - 13:31
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The issue is, without multicast enabled, the router works OK. Within minutes of enabling multicast on the router and interfaces, the router stops accepting telnet connections, stops routing out except for next hop directly connected IP, then EIGRP starts to flap, eventually all routing stops. We have other routers with the same hardware, same version IOS, and same configuration that are working just fine.


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