5

If a Red Hat or other Linux host has a conflict with an IP address, is there a way to have it display a warning message on the console or in a log, like Windows and MacOS do?

i.e. my computer has an IP address configured (or received from a DHCP server) but finds another device on the network using the assigned address. Will it log the conflict?

17

IP Conflict detection is standardised in RFC 5227. One Linux tool that implements it is IPwatchd, which has a GNOME notification component (ipwatchd-gnotify).

  • +1 - i've never heard about that standard; thanks! – pQd Apr 28 '10 at 14:51
9

you can use arpwatch to find out about ip conflicts on ethernet segment you are connected to. it will alert about unseen ip-mac combinations or whenever such association change.

  • It also warns when it sees one box using multiple IPs. False positives ftl :(. – sourcejedi May 28 '13 at 16:24
1

I don't know the exact mechanisism of how it does it, but I've seen warnings in CentOS when bringing up a network device along the lines of "Failed to bring up eth0, a device on the network already has this IP".

1

You can use the arping command to detect conflicts over a specific IP address:

arping -I eth0 192.0.2.1

You may find multiple MAC addresses replying for that specific IP address.

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