Finding IP Address of Device Using Cisco Switch and Router


I had a Raritan PDU that was plugged into a Cisco 2960 switch which in-turn was connected to a Cisco 6506 router. The PDU did not display the IP address and I could see it was plugged into port 24 on the switch.



To find out the IP address


Log into the Cisco 2960 switch:

– Telnet/SSH to the switch


Find the MAC address:

#show mac-address-table interface fastEthernet0/24

          Mac Address Table

Vlan    Mac Address       Type        Ports
—-    ———–       ——–    —–
  99    000d.5d0b.b9d5    DYNAMIC     Fa0/24
Total Mac Addresses for this criterion: 1



Now I have the MAC address I can check to see if this shows up on the 6506 router:

– Telnet/SSH to the router


Use the following command with the MAC address from the previous step:

#show arp | includ 000d.5d0b.b9d5

Internet          221   000d.5d0b.b9d5  ARPA   Vlan99