How discover duplicate IP using Ubuntu? (is it possible to have duplicate ip?)
Solution 1:
You can use arpping command. The arping utility performs an action similar to ping command, but at the Ethernet layer. You can send ARP REQUEST to a neighbor host / computers.
Send ARP request
find out reachability of an IP on the local Ethernet with arping i.e send ARP request 192.168.1.1:
$ sudo arping -I eth0 -c 3 192.168.1.1
Output:
ARPING 192.168.1.1 from 192.168.1.106 ra0
Unicast reply from 192.168.1.1 [00:18:39:6A:C6:8B] 2.232ms
Unicast reply from 192.168.1.1 [00:18:39:6A:C6:8B] 1.952ms
Sent 3 probes (1 broadcast(s))
Received 3 response(s)
Where,
Find duplicate IP
The -D option specifies duplicate address detection mode (DAD). It returns exit status 0, if DAD succeeded i.e. no replies are received.
$ sudo arping -D -I eth0 -c 2 192.168.1.1
If 192.168.1.1 duplicated you should see zero exit status:
$ echo $?
Always use following syntax for duplicate address detection with arping:
$ sudo arping -D -I <interface-name> -c 2 <IP-ADDRESS-TO-TEST>
$ echo $?
Solution 2:
You can install IPwatchD which works with (other) Debian packages.
The linked article also explains the method and installation steps.
IPwatchD source is from sourceforge.
It lets you configure for a GUI notification (as above, only for GNOME) and a 'syslog' message.