[c-nsp] Invisible CDP neighbours

[Phil Mayers]

Bah. 2 out of 9 two boxes, we decide to get vendor rather than TAC
maintenance, and it all goes wrong... I wonder if it's encoded in the
backplane PROM ;o)

Whilst I'm waiting for my reseller to embarass themselves; we have the
following setup:

 core1  [Te1/1] --- [Te1/1] core2
[Te1/3]                    [Te2/3]
   |                          |
   |                          |
[Te1/1]                    [Te1/1]
 new-1  [Te1/2] --- [Te1/2] new-2

core1/core2 are old/existing routers; 6500 sup720-3B 12.2SXF10 and SXF6
respectively, 6704 w/ DFC-3B. They can see each other *and* new-1/2 on
the correct ports with CDP.

new-1/2 are new, 6500 sup720-3B 12.2SXF10, 6704 w/ CFC (i.e. no DFC) and
ACE20 (currently unused). They can see no CDP neighbours on their 10gig
ports.

The 10gig ports are configured more or less identically on all 4
routers, and a "debug cdp blah" on core1/core2 shows they think they are
emitting the CDP packets, but similar debug on new-1/2 never shows a
receive.

Weirdly, all 4 are connected to an out-of-band 10/100 network via the
sup gi5/2 port, and can see each other just fine.

I'm having a hard time believing 6704 needs a DFC to do CDP correctly;
the only other differences are minor hardware revisions (the new routers
are sup 5.4 as opposed to 4.4).

Double oddness; "sh udld" has valid data in the "CDP device name" space,
which is just annoying!

Any thoughts?