Hi everyone i have a question, i have a device connected to the port in the Core switch, It's for LAN connected to Secomia device and the LAN port is configured and we checked in the firewall we see it connected. i'm wondering why this LAN port is not having a mac address when i did show mac address table in the switch :( ?

  • 2
    Is it sending traffic?
    – Ron Trunk
    Sep 29, 2022 at 20:03
  • The core switch only records MAC addresses that are directly plugged in to its ports. Oct 29, 2022 at 21:04
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
    – Ron Maupin
    Nov 19, 2022 at 22:57

1 Answer 1


A switch's source address table is populated by any frame it receives. If there's no MAC association on a port, then no valid frame has been received after link up. Invalid frames include ones with an invalid source address or tagged for a disallowed/unconfigured VLAN.

You could use SPAN port monitoring to capture that port's traffic in order to find out what's going on there.

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