[c-nsp] Identifying device(s) connected to cisco L2-only switch

[Dale Shaw]

Hi all,

Here's the scenario:

- L2 switchport in cat3750 "up/up"
- No MAC learnt on the interface ("sh mac-addr int gi1/0/4" shows no
dynamic MAC address)
- Attached device not necessarily configured with an IP in the correct
VLAN (mismatched with switchport) - endpoint IP configuration unknown

I haven't really given this much consideration, but does anyone know
of any tricks, ideally executed _from_ the switch, to encourage the
attached device to spit back a frame? Essentially I want/need to
figure out what's attached. Even knowing the MAC vendor would help.

Other suggestions are welcome. I guess I could try things like a
broadcast ping from a host in the same VLAN, make the port a trunk and
madly ping sweep, but something more elegant would be nice.

A physical inspection, in this case, is not possible.

cheers,
Dale