Sanity check... My machine is sitting behind a router that forwards all HTTP,HTTPS,and SSH requests to my server. I'm also running a MySQL database, CUPS, and SENDMAIL but those work locally on the server so there is no need for the router to forward those requests. Because these services are working locally I don't think it is necessary to define them in the "TCP rules" section below. I need a good pair of eyes to look at this one since I am an iptables newbie. Also what is the difference between iptables and ip6tables?

# IPTables Script

# (1) Policies (default)
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP

# (2) User-Defined chain for ACCEPTed TCP packets
iptables -N okay
iptables -A okay -p TCP --syn -j ACCEPT
iptables -A okay -p TCP -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A okay -p TCP -j DROP

# (3) INPUT chain rules

# Rules for incoming packets from the LAN
iptables -A INPUT -p ALL -i eth0 -s 192.168.0.0/8 -j ACCEPT

# Packets for established connections
iptables -A INPUT -p ALL -d 192.168.0.100 -m state --state ESTABLISHED,RELATED -j ACCEPT

# TCP rules

# SSH
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 22 -j okay
# HTTP
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 80 -j okay
# IDENTD (Necessary for IRC ?????)
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 113 -j okay
# HTTPS (SSL)
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 443 -j okay
# IPP
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 631 -j okay
# MySQL
iptables -A INPUT -p TCP -i eth0 -s 0/0 --destination-port 3306 -j okay


# UDP rules
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 2074 -j okay
iptables -A INPUT -p UDP -i eth0 -s 0/0 --destination-port 4000 -j okay


# ICMP rules
iptables -A INPUT -p ICMP -i eth0 -s 0/0 --icmp-type 8 -j ACCEPT
iptables -A INPUT -p ICMP -i eth0 -s 0/0 --icmp-type 11 -j ACCEPT

# (4) OUTPUT chain rules
# Only output packets with local addresses (no spoofing)
iptables -A OUTPUT -p ALL -s 127.0.0.1 -j ACCEPT
iptables -A OUTPUT -p ALL -s 192.168.0.100 -j ACCEPT
iptables -A OUTPUT -p ALL -s 68.46.153.117 -j ACCEPT

1) Your router is on the network 192.168.0.0/8, so by accepting all traffic from that network, you are accepting all traffic from the router also and hence, all traffic from the internet. This of course assumes your router is on eth0.

2) ip6tables is iptables for the IPv6 protocol.

Well the routers public IP address is the one given to me by my ISP. Its something like 68.46.34.129 . From the LAN the routers IP is 192.168.0.1 . I see what you are saying. Isn't this how I want it setup though. It does allow everything from the router in but then it runs through the rest of the rules doesn't it check to make sure that they are valid requests to the server?

Okay I found a new problem with these iptables rules. For some reason I am unable to print while these rules are in effect. I have opened port 631 (IPP). I use CUPS for printing.

Does CUPS use UDP packets? I'm sure I'm missing something very simple here.