Firewall Run Level?

Hey All I was wondering which run level to run a firewall/router? Run level 2 or 4. This will be a internet connected, (practice box). tksysv or ntsysv? Should I use the SuSEfirewall2, or write my own iptables? All advise will help. Thanks, Invalind Addr3ss -- Q) What do you get when you mix a spammer with a hacker? A) A Spacker