Running Quake 3 server behind a firewall

[robian]

I considered posting this to the network forum. However I believe this question directly relates to Quake 3 and not to generic networking issue. I hope I judged correctly.

Is it possible to run a Quake 3 linux server on an average dsl-line, using an iptables firewall (shorewall) to shield the local boxes from the internet?

My setup:
- Alcatel Speedtouch modem/router that forwards everything to my firewall. (I am lead to believe this is the case: I have enabled use default host for incoming traffic)

- Debian box running shorewall, connected to the Speedtouch and:

- a bunch of local boxes, one of which I'd like to use as the Q3 server. This pc can be booted into Gentoo or Debian. I share my games dir between these two systems.

All my local systems are in the same zone. For brief periods I open some ports to enable outside access to httpd on one of my local boxes or to enable X forwarding. This works. I was hoping that running a Q3-server would not be very much more difficult. I have openend a range of udp ports from 27960 onwards. All locally originating traffic is allowed. I can connect to Q3-servers on "the internet" and I can connect to my locally running Q3-server.

When outside Q3-clients try to connect, I see firewall messages, that look a lot like the one in a FAQ-entry. I am not able to use this information to solve my problem.

It mentions a broken implementation wrt NAT en IMCP. I am not sure which implementation is broken. Is it the Q3-server, the Q3-clients, my firewall, my modem/router....??

I hope someone is able to give some hints how to get this solved. I have a feeling that my firewall settings are correct, but if something special is required to enable forwarding and allowing Quake 3 connections, I'd like to hear it.