[Nagios-users] detect 2 DHCP Servers on network?

[Hari Sekhon]

I was wondering what the best way of detecting a rogue dhcp server on
the network is.


I ask because some idiot at work installed vmware with it's dhcp server
which stuffed the company laptops which rely on dhcp since they got sent
to the wrong subnet.

Nagios actually drew my attention to this when troubleshooting because
it said 2 DHCP offers received.

I'm thinking about writing a shell wrapper to parse the output from the
check_dhcp plug-in and raise a warning status if it returns more than 1
dhcp offer.

Any other ideas?


Hari

[Eli Stair]

Use CPAN's Net::DHCP::Packet to quickly create a DHCPDISCOVER packet, and
IO::Socket::INET to read raw incoming data to port 68, count the number of
DHCPOFFER's you get. Set your script output to proper OK/WARN/CRIT state
and the number/names of "rogue" servers in the text.

Just a suggestion.

/eli

Post by Hari Sekhon
I was wondering what the best way of detecting a rogue dhcp server on
the network is.
I ask because some idiot at work installed vmware with it's dhcp server
which stuffed the company laptops which rely on dhcp since they got sent
to the wrong subnet.
Nagios actually drew my attention to this when troubleshooting because
it said 2 DHCP offers received.
I'm thinking about writing a shell wrapper to parse the output from the
check_dhcp plug-in and raise a warning status if it returns more than 1
dhcp offer.
Any other ideas?
Hari
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