How do I find an unknown IP address?

Download Wireshark from

Plug into the switch with the CompactLogix. Start capturing with Wireshark. Cycle power to the CompactLogix.

Type the letters “arp” into the Display Filter field in Wireshark and hit Enter. You’ll see the CompactLogix broadcasting its IP address upon bootup, to confirm that there are no other devices on the LAN with that IP and to populate the MACID tables of the connected switches.

There are other threads about this; search on “Wireshark” and “ARP”.