Determining the port to which a system is connected by MAC address

If you need to know the port on a Cisco switch to which a particular host is connected and know the media access control (MAC) address, you can determine the port to which it connects using a show mac address-table address command. You can view all of the entries in the MAC address table with the command show mac address-table, but if you know the MAC address of the relevant system and only wish to determine the port on the switch to which it connects, you can specify its MAC address with the command show mac address-table address followed by the 48-bit MAC address, which can be in the form xx.xx.xx.xx.xx.xx or xxxx.xxxx.xxxx .
Saturn>show mac address-table address 50:e5:49:d8:13:37
          Mac Address Table

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   1    50e5.49d8.1337    DYNAMIC     Fa0/19
Total Mac Addresses for this criterion: 1

With the port number, you can determine details for the interface to which the system connects using a show interfaces port where port is the port identified by the show mac address-table address command.

Saturn>show interfaces Fa0/19
FastEthernet0/19 is up, line protocol is up (connected)
  Hardware is Fast Ethernet, address is 0009.e897.d293 (bia 0009.e897.d293)
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, media type is 100BaseTX
  input flow-control is unsupported output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:05:39, output 00:00:00, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     1322485 packets input, 794024170 bytes, 0 no buffer
     Received 3229 broadcasts (2334 multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 2334 multicast, 0 pause input
     0 input packets with dribble condition detected
     1316400 packets output, 587905740 bytes, 0 underruns
     0 output errors, 0 collisions, 2 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out



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