Posts tagged arping

arping: duplicate ip address detection

posted on 2016-03-31 22:50

Duplicate IP's within your subnet are a problem that you can detect via arping. It sends a layer2 ARP REQUEST to detect if an IP is already known within the network.

Usually only this is sufficient for usage from the shell:

arping -D <IP>`

When you simply receive a response on the commandline, the IP is in use already. If you use vlans, you have to specify your interface with -I, too.

If you want to use this from within scripts, you might want this:

arping -D -w2 -c2 -I <INTERFACE> <IP>
echo $?

arping returns zero if there's exists a duplicate IP.

One thing to keep in mind is that some linux distributions have several packages available, but only one it the arping. See on debian, for example, you got these two on jessie:

arping/stable 2.14-1 amd64
  sends IP and/or ARP pings (to the MAC address)

iputils-arping/stable,now 3:20121221-5+b2 amd64 [installed]
  Tool to send ICMP echo requests to an ARP address

You need the iputils-arping one, if you happen to use debian.

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