Linux – Monitor DNS queries of all hosts in LAN

Make sure nsupdate is installed, then use it to register your names. The one problem with nsupdate is that you are going to need to permit non-secure dynamic updates. Unless your platform supports nsupdate-gss, and your linux machines are setup with kerberos to be part of the domain.

I have a script that looks like somewhat like this I use in a couple situations, like dynamic registration of OpenVPN clients. In the real script, the IP and actual hostname comes from the vpn server. If you are using a Debian based distribution it would be pretty easy to tweak this script and place it in /etc/network/if-up.d/.

#/bin/bash

dnssrv="192.168.47.12"   # the dns server that will accept the ddns request.
zone="dyn.example.org"   # the name of the zone
ttl="7200"               # 
hostname=`hostname`      # the name of your local host
ip='192.168.47.193'      # IP of the host

(
 echo "server ${dnssrv}"
 echo "zone ${zone}"
 echo "update delete ${farm}"
 echo "update add ${hostname}.${zone} ${ttl} A ${ip}"
 echo "send"
) | /usr/bin/nsupdate

Another alternative may be to just use DHCP for both interfaces at to setup reservations.