Discover the device connected to a Layer 3 Cisco Switch Port using MAC Address to IP Address Mapping

by | Jul 30, 2013 | IT Tips | 0 comments

You need to ping the device from the switch so you can populate the switches arp cache with the IP/Mac mapping.

From there you can then find the port

# firstly on the cisco switch you need to ping the IP address of the device

ping 192.168.0.6
Sending 5, 100-byte ICMP Echos to 192.168.0.70, timeout is 2 seconds:

!!!!!

# you can grab the mac address connected to a cisco switch port

switch01#show mac-address-table | include Gi0/6
   1    d4be.d9fb.8630    DYNAMIC     Gi0/6

# and get the IP Address of the connected device
switch01#show ip arp | include d4be.d9fb.8630
Internet  192.168.0.6             0   d4be.d9fb.8630  ARPA   Vlan1

This may only work if the host you are trying to track down is doing inter-subnet communications.

You may need to do a ping or nmap -sP subnet/subnet_mask to populate the mac-address-table on the switch.

YMMV

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