switchport identification...

use sh ver to find the mac address assigned to a switch...

sw2950_02#sh ver
Cisco Internetwork Operating System Software
IOS (tm) C2950 Software (C2950-I6K2L2Q4-M), Version 12.1(22)EA14, RELEASE SOFTWA

Processor board ID FHK0619X14J
Last reset from system-reset
Running Standard Image
24 FastEthernet/IEEE 802.3 interface(s)

32K bytes of flash-simulated non-volatile configuration memory.
Base ethernet MAC Address: 00:09:B7:3F:CE:80


so what is the mac of port 1?

sw2950_02#sh int fa0/1
FastEthernet0/1 is up, line protocol is up (connected)
  Hardware is Fast Ethernet, address is 0009.b73f.ce81 (bia 0009.b73f.ce81)

how about fa0/10? better know hex...

sw2950_02#sh int fa0/10
FastEthernet0/10 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0009.b73f.ce8a (bia 0009.b73f.ce8a)

15 is easy...

sw2950_02#sh int fa0/15
FastEthernet0/15 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0009.b73f.ce8f (bia 0009.b73f.ce8f)

16 is not...

sw2950_02#sh int fa0/16
FastEthernet0/16 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0009.b73f.ce90 (bia 0009.b73f.ce90)

the ten's position incremented by one remainder zero is fa0/16...


which makes fa0/24 easy... what is 16 plus 8...

sw2950_02#sh int fa0/24
FastEthernet0/24 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0009.b73f.ce98 (bia 0009.b73f.ce98)