Configuring FreeBSD IPFilter with ICQ:

The firewall rules:

/etc/ipf.rules

pass in quick on tun0 proto tcp from any to any port 24500 >< 24505 flags S
keep state

The port forwardings:

/etc/ipnat.rules

rdr tun0 0.0.0.0/0 port 24500 -> 192.168.100.70 port 24500
rdr tun0 0.0.0.0/0 port 24501 -> 192.168.100.70 port 24501
rdr tun0 0.0.0.0/0 port 24502 -> 192.168.100.70 port 24502
rdr tun0 0.0.0.0/0 port 24503 -> 192.168.100.70 port 24503
rdr tun0 0.0.0.0/0 port 24504 -> 192.168.100.70 port 24504
rdr tun0 0.0.0.0/0 port 24505 -> 192.168.100.70 port 24505