How to track down duplicate MAC addresses out of the ARP table dump?

Use this easy parsing command using uniq to pull duplicates out of the arp table dump that you can grab from your routers.

cat arp_dump_XXXXXXXXX.txt | awk ‘{print $1″ “$3}’ | uniq -D -w 17

That gives you the duplicates from row 1 and the read out of row 3 which is the IP address and Name.

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