How to: find the Switch and Port You are connecting to

[chicagotech]

You can use show mac-address-table address xx-xx-xx-xx-xx-xx command line.

For example, we have 10 switches in our main building. I would like to setup one port in the classroom to static IP.

1. Find my laptop Mac address by using ipconfig /all. It is 00-16-D4-BA-D7-77
2. Telnet one of the switch and enable it.
3. Type “show mac-address-table address 00-16-D4-BA-D7-77”, it display

Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
---- ----------- -------- -----
1 0016.d4ba.d777 DYNAMIC Gi0/50
Total Mac Addresses for this criterion: 1

4. The Gi0/n (Gi0/50 in our case) indicates you are connecting to a gigabit port that is connecting to other switches. You need to use CDP (Cisco Discovery Protocol) to locate another switch.


show cdp neighbor Gi0/50 detail
-------------------------
Device ID: chicagotech_10
Entry address(es):
IP address: 10.0.20.46
Platform: cisco WS-C3560-24PS, Capabilities: Switch IGMP
Interface: GigabitEthernet0/50, Port ID (outgoing port): GigabitEthernet0/1
Holdtime : 149 sec


5. telnet 10.0.20.46

6. show mac-address-table address 00-16-D4-BA-D7-77
Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
---- ----------- -------- -----
1 0016.d4ba.d777 DYNAMIC Gi0/2
Total Mac Addresses for this criterion: 1
REG_TELE_3560_10#show cdp neighbor Gi0/2 detail
-------------------------
Device ID: chicagotech_1
Entry address(es):
IP address: 10.0.20.18
Platform: cisco WS-C3750G-12S, Capabilities: Switch IGMP
Interface: GigabitEthernet0/2, Port ID (outgoing port): GigabitEthernet1/0/6
Holdtime : 140 sec


7. The switch you are connecting is 10.0.20.18 and the port is Gi0/2.

[guest]

We had a case that two computers were using the same IP addresses. I followed this instruction to find the another computer.

What I have learned is that you may need to use show mac-address-table address and show cdp neighbor many times until show cdp neighbor doesn't show next switch.

[chicagotech]

If “show mac-address-table address 00-16-D4-BA-D7-77” doesn't work, you may try this ####.####.####, for example,

show mac-address-table address 001f.29bc.840c
Non-static Address Table:
Destination Address Address Type VLAN Destination Port
------------------- ------------ ---- --------------------
001f.29bc.840c Dynamic 200 FastEthernet0/12
3548_IP2049#