DNSmasq

[JCircle]

This is more of a hack than a fix, but sometimes can work and i would have to play around and make sure it works, ill do this tonight.

You can fake the system into thinking it IS the external IP address.

ifconfig
eth0 192.168.0.100 <-- internal
eth0:1 172.21.21.21 <--- external

set your routing to use eth0 gateway and all
map your firewall holes to your 192.168.0.100 ip
your dns should answer back with your external ip address as well as apache vhosts should work.

Ill test this tonight using the current build but I have used this work around for a 3rd dns server before.

NOTE: this is a single server build, already noted this is a quick hack to make something work, (before you flame it )