From: shiran guez (shiranp3@gmail.com)
Date: Tue Mar 27 2007 - 17:58:28 ART
Hi Malcom
Some points as it is late and I am just giving you a hedding:
EIGRP/ OSPF/ RIP (Ver2) ...
use multicast non-routeable address 224.0.0.1 - 225.0.0.254 meaning in all
the packet the Source will be the router that you are sniffing on and
Destination will be the Multicast address as Multicast is not a Source and
if the Destination was unicast this was either due to specific configuration
or you where not using IGP
EIGRP 224.0.0.10
OSPF 224.0.0.5 (all routers) 224.0.0.6 (DR/BDR)
RIP (224.0.0.9)
and so on
regarding the routes are not reachable this is a whole other storry for next
time, regarding the packet format you can find it in Cisco Documentaion site
or in easy Google Search.
Regards,
Shiran Guez
On 3/27/07, Malcolm Price <malcolm.price@lanbase.com> wrote:
>
> Hi group,
>
>
>
> Has anyone ever seen a case whereby you have two catalysts (3560 L3)
> running
> eigrp on the same LAN. Cat A and Cat B form adjacencies and exchange
> hello's. However when cat B receives cat A's routes all the routes learned
> from A are stamped as destination unreachable.
>
>
>
> I've put a sniffer trace on router B and inspected the eigrp update
> packets
> entering router B.
>
>
>
> The source IP of the packet entering CAT B is 10.1.1.1 (cat A) and the
> destination IP address is the multicast address, 224.0.0.10. However, I
> would expect this destination address to be 10.1.1.2 (Cat B) ?.
>
>
>
> In the IP EIGRP UPDATE packet entering router B the details are:
>
>
>
> IP Internal Route = 10.2.0.0/16 - Destination unreachable
>
> Type = 0x0102 (IP Internal Route)
>
> Size 27 bytes
>
> Next Hop = 0.0.0.0
>
> Metrics etc
>
> Prefix = 16
>
> Destination = 10.2.0.0
>
>
>
> The route 10.2.0.0/16 is being advertised by Catalyst A. This is a valid
> subnet local to Cat A.
>
>
>
> The eigrp configuration itself is pretty simple,
>
>
>
> Router eigrp 254
>
> Network 10.0.0.0
>
> No auto-summary
>
>
>
>
>
> I could understand the next hop set to 0.0.0.0 if this was being
> advertised
> OUT by Cat B as this would be self/the origin but this is a packet being
> Received into Cat B which doesn't add up.
>
>
>
> Does anyone have a description of the EIGRP packet format and perhaps an
> explanation why the route is flagged as unreachable.
>
>
>
>
>
> Many thanks in advance,
>
> Malcolm
>
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-- Shiran Guez MCSE CCNP NCE1 http://cciep3.blogspot.com
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