Other things we allow

• IRC servers like to probe for ident, lets let that through so I can get on EFNet. This rule allows ident: iptables -A INPUT -i eth0 -p tcp -s 0/0 -d 0/0 --dport 113 -j ACCEPT

• We want to allow ICMP in if it is related to some other connection (aka, traceroute). This rule allows that: iptables -A INPUT -i eth0 -p icmp -m state --state ESTABLISHED,RELATED -j ACCEPT

• Guess what I'm going to say. Yup. One rule, line wrapped.

• I've also got an infobot running on my server, and it wants a port open so I can telnet to it. This rule lets me do that: iptables -A INPUT -i eth0 -p tcp -d 0/0 --dport 8676 -j ACCEPT

• You probably aren't running an infobot, but this rule is an excellent example of opening a TCP port.

• One last allow: For DCC connections to work, we need to let in all “RELATED” TCP connections. DCC is such a crappy protocol, but this rule will allow it: iptables -A INPUT -i eth0 -p tcp -m state --state RELATED -j ACCEPT

Notes: