[c-nsp] CDP over ATM

[rbf+cisco-nsp at panix.com]

On Tue, Feb 01, 2005 at 09:09:39PM +0100, Gert Doering wrote:
> Hi,
> 
> On Tue, Feb 01, 2005 at 09:04:13PM +0100, Gert Doering wrote:
> > Cisco#sh cdp nei atm2/0.36
> > ...
> > Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
> > Cisco-XXX-XX-temp
> >                  ATM2/0.36          170          R        1603      Eth 0
> > 
> > hooray! :-)
> 
> ... interesting enough, the router on the *other* end doesn't see the
> CDP packets (ATM-VC -> bridging DSL modem -> Ethernet -> Cisco).   Can't
> say whether the CDP packets aren't sent, or whether the DSL modem is
> eating them.

CDP over ATM is likely encapsulated directly in ATM; for what you
describe above to work, you'd need the CDP packets to be encapsulated
in bridged ethernet packets.  (That is, you want CDP over Bridged
Ethernet over ATM, not CDP over ATM.  Or, put another way, you want
"atm route-bridged cdp", which doesn't actually exist.)

It works in the reverse direction because the router is (presumably)
being liberal in what it receives, so CDP packets are accepted whether
they are natively encapsulated or encapsulated in Ethernet.

     -- Brett