sh cdp neighbor

gojericho0

Quick question, does the following output imply that there is a hub connected to int fa 0/10? The reason i'm thinking this is because cdp is a l2 protocol and I see two responses coming from this interface, one for a switch and the other for a router.

Wayne_LAN2950_12B#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone

Device ID Local Intrfce Holdtme Capability Platform Port ID
WAYNE Fas 0/10 156 R 2621XM Fas 0/1
Wayne_LAN2950_12A
Fas 0/10 130 S I WS-C2950-1Fas 0/10
Wayne_LAN2950_12A
Fas 0/12 130 S I WS-C2950-1Fas 0/12
Wayne_LAN2950_12A
Fas 0/11 130 S I WS-C2950-1Fas 0/11

bighornsheep

Not necessarily, notice that the CDP entry from the 2621 is older than the entries from the 2950, when the CDP holdtime lapse, you may see that the 2621 purges, meaning it was "plugged in" and then it was unplugged again.

gojericho0

Hi BigHornSheep, I was thinking that as well, but i've been looking at this for about 2 days now and they are both constantly there

dtlokee

It would typically indicate there is some non-Cisco hub or switch connected to interface fa0/10, not just a hub. Non-Cisco gear will see the CDP frames as "traffic" and forward it to all interfaces (because it's multicast, which is treated by most switches and hubs as broadcast.)

gojericho0

Thanks dtlokee! That makes sense