Packets being dropped at the gateway

[Carl Hultquist]

One of my friends and I recently compiled iptables with full NAT and
filtering support into the 2.4.10 kernel on his machine in order for me
to access the world outside of our local network. On the whole, this
works quite well, except we've had some trouble with ICQ: occasionally
messages meant for me end up getting received by my friend (whose
machine is the gateway) and not me. This doesn't always happen though,
which is what we can't understand, especially since everything else
(HTTP, FTP, SMTP, IMAP, DNS) seems to work just fine (well, there
haven't been any other adverse effects on my friend's machine yet...)

The only entry which we have made into the ip-tables is the following
(as per the NAT-HOWTO under the small section describing how to quickly
configure masquerading):

iptables -t nat -A POSTROUTING -o eth0 -s <my_address> -j MASQUERADE

where <my_address> is the ip-address of my machine on the local network.

I remember that there were special modules for ipchains to support
things like ICQ, mIRC DCC connections, etc. Can those be used with
iptables? If so, where are they available? If not, is there a simple
solution to my problem?

Cheers

Carl