I don't believe this is correct. Several Cisco sources say "Cisco devices
never forward a CDP packet" (e.g. CIT course notes, and I've seen it in
other places as well). In our network, we have many instances of router
<-> switch <-> router (all Cisco, all on the same network). The routers
can see the switch via CDP, and the switch can see both routers, but the
routers cannot see each other via CDP although they are in the same LAN.
But yes, a dumb hub connected on the port (or possibly a non-Cisco switch?)
can show several Cisco devices on the same port. We have instances of that
too :-)
JMcL
---------------------- Forwarded by Jenny Mcleod/NSO/CSDA on 29/11/2000
12:26 pm ---------------------------
Priscilla Oppenheimer <[EMAIL PROTECTED]>@groupstudy.com on 29/11/2000
08:35:27 am
Please respond to Priscilla Oppenheimer <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
To: "Nabil Fares" <[EMAIL PROTECTED]>
<[EMAIL PROTECTED]>
cc:
Subject: Re: CDP protocol
A CDP-enabled interface learns about all other CDP-enabled devices on its
LAN, so I'm not sure why you would wonder about it learning about the C5505
and the 1900. CDP messages are sent to a data-link-layer multicast address
that traverses switches. Maybe the 1900 is behind the C5505. Without more
information on your topology, it's hard to give a more definite answer.....
Priscilla
At 03:11 PM 11/28/00, Nabil Fares wrote:
>Greetings,
>
>I've an interesting one for you guys. When I issue a "sh cdp neigh"
command
>on a 25XX router, I get 2 devices (WS-C5505 and 1900) on the same E0
>interface. The destination port for the 5505 is 3/8, and the 1900 is B.
I
>don't really have physical access to the equipment for visual inspection.
>Could there be a dump hub between the switches? since a dump hub doesn't
>have a MAC address, the cdp protocol is showing both devices instead!
>
>Any help on this one guys is appreciated.
>
>Thanks,
>
>Nabil
>
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________________________
Priscilla Oppenheimer
http://www.priscilla.com
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