Couple of things here:
1- If you know the port to which the client is connected then below is the command to check the mac address;
Switch#sh mac address-table interfaces f0/1 >>> F0/1 is the port were client is connected
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
1 0060.2fa6.d402 DYNAMIC Fa0/1 >>> MAc address is seen.
2-
Switch#sh mac-address-table >> This will give complete mac address list with port-numbers which are connected or learned on this particular switch.
3- If you know the ip address of the client then you can get the mac address:
Switch#sh ip arp 192.168.1.1
Protocol Address Age (min) Hardware Addr Type Interface
Internet 192.168.1.1 0 000d.28a9.d400 ARPA Vlan20 >>>> Mac address seen.
Then to get the port of that particular mac:
sh mac address-table address 000d.28a9.d400 >> This will give you the port number on which this mac address has been learned.
HTH
Regards
Inayath
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