Hawk is a web based utility for monitoring and comparing hosts on your
network with what is in DNS.  Hosts that are answering pings but are not
in DNS may be unauthorized, and addresses in DNS which are not answering
may be able to be reclaimed.  Hawk monitors all hosts on the networks
you specify and lets you view them via a web page.

Hawk consists of a backend written in Perl that monitors hosts by ICMP
pings and writes the status to a mysql database.  The frontend is in
PHP and lets you select which network to view, and how to view it.

This version has several enhancements to the original; including cleaner
Perl code, a user-definable string to designate unused addresses that
are in DNS, testing that the forward and reverse hostnames match, and
the daemon forks one process pre subnet.

WWW: http://sourceforge.net/projects/iphawk/