SuSEfirwall | snort & portforwarding

Hi list! We are using SuSE packetfilter for our firewall. I'm planning to forward some ports to another machine, so my question is does the "packetfilter" protect the other machine on these ports or do I have to run another packetfilter on the forwarded ports? Is it the same problem within snort, so port forwarding is in a "higher priority" than any sniffer or filter in linux ... thank you, turtle