[nsp] IP-EIGRP: Neighbor A.B.C.D not on common subnet...

[Thomas Renzy]

Yuval,

Do you have an EIGRP neighbor on this segment with a secondary interface
configured? I've seen this type of message when, on an Ethernet segment, an
EIGRP neighbor has a secondary interface configured on one router, but not
on another router on the same Ethernet segment.

EIGRP hello packets have a TTL of 2, so I don't think it traverse the next
hop. 

Thanks,
Thomas Renzy 
IS&T Global Network Services
VERITAS Software
Office: +650-527-4734
Mobile: +650-996-7048
Fax: +650-527-2034

"Some people drink from the fountain of knowledge, others just gargle." -
Author Robert Anthony



-----Original Message-----
From: Yuval Ben-Ari [mailto:yuvalba at netvision.net.il]
Sent: Sunday, January 26, 2003 3:11 AM
To: cisco-nsp at puck.nether.net
Subject: [nsp] IP-EIGRP: Neighbor A.B.C.D not on common subnet...


Hi,

I noticed messages of the above kind while logging to a router and
issuing 'term mon':

Jan 26 13:01:59.566 IST: IP-EIGRP(Default-IP-Routing-Table:1680):
Neighbor A.B.C.D not on common subnet for FastEthernet0/0

Obviously the message means the router is seeing EIGRP hello packets
coming on the interface from a neighbor which is not on that interface's
subnet, which happens to be correct.
However I have no idea how these packets get to the interface as it is
not on the same L2 segment (different VLAN).
The error is only reported on terminal and not on all routers (seems to
be IOS dependent + 'eigrp log-neighbor-warnings' command)

Is it possible the hello packet is transiting a L3 device ?

Will be happy to hear your ideas.

Thanks.

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