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

[Yuval Ben-Ari]

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.