Tuesday, October 23, 2018

Sticky MAC address on one port preventing that computer from connecting on a different port

We have port security enabled on a small handful of ports that are "public" facing (i.e. ports in the lobby that you don't need a key card to reach). Today we had a new person sitting at the front desk for a little while so I increased the maximum number on that port by 1 which allowed her laptop to connect and everything was fine.

When she went back to her normal desk she was unable to fully connect via ethernet. The same switch stack is used for the entire first floor office area which includes the front desk and her own desk. Her laptop was getting a DHCP lease including an IP, gateway, dns, and all that but it was unable to ping any addresses in any subnet (her own or otherwise).

During this time I tested plugging her computer into a port on the 2nd floor, which is a separate switch stack, and it worked fine.

The thing that eventually fixed it was to remove her MAC address sticky entry from the lobby port. I haven't been able to figure out why the issue occurred in the first place though. Has anybody seen this before?

She was the 5th MAC address to be added to the lobby port and the other 4 have not had any issues like this.



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