This is to follow up this first discussion
https://supportforums.cisco.com/message/3874525#3874525
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While performing troubleshooting for
https://supportforums.cisco.com/message/3874519
I realized the 3750 switch does not learn MAC address from LLDP multicasts generated every 30 seconds by end device connected to the port .
It surprised me, not sure if this is expected behaviour or not. It is not dependent on if port security is set or not.
For the issue above I had a Polycom IP phone connected to the port. It generates LLDP multicast every 30 seconds, but does not do anything else.
The switch sees the phone as LLDP neighbour, but does not learn its MAC address.
I reproduced this scenario later on with Cisco switches only, 'works' the same way.
Does anyone know is this expected or a bugy behaviour ?
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I've performed several other tests and think the answer above might not be Cisco-wise correct.
I tested on WS-C3560CG-8PC-S and this switch learns the MAC address from the LLDP multicast.
I tested also on this stack
-- ----- ----- ---------- ----------
* 1 54 WS-C3750X-48P 12.2(55)SE6 C3750E-UNIVERSALK9-M
2 54 WS-C3750X-48P 12.2(55)SE6 C3750E-UNIVERSALK9-M
3 52 WS-C3750-48P 12.2(55)SE6 C3750-IPBASEK9-M
4 52 WS-C3750-48P 12.2(55)SE6 C3750-IPBASEK9-M
5 52 WS-C3750-48P 12.2(55)SE6 C3750-IPBASEK9-M
6 52 WS-C3750-48P 12.2(55)SE6 C3750-IPBASEK9-M
and can see ports on 3750X learn MAC address from LLDP multicast, but on WS-C3750-48P not. This looks like an inconsistency or a Cisco bug.
Does anyone have an authoritative answer if a Cisco switch is supposed to learn a MAC address from a LLDP multicast ?
Thank you,
Vlad
