Information
Configure the firewall rules for new outbound, and established connections.
Rationale:
If rules are not in place for new outbound, and established connections all packets will be dropped by the default policy preventing network usage.
Note: Changing firewall settings while connected over network can result in being locked out of the system.
Solution
Configure iptables in accordance with site policy. The following commands will implement a policy to allow all outbound connections and all established connections:
# iptables -A OUTPUT -p tcp -m state --state NEW,ESTABLISHED -j ACCEPT
# iptables -A OUTPUT -p udp -m state --state NEW,ESTABLISHED -j ACCEPT
# iptables -A OUTPUT -p icmp -m state --state NEW,ESTABLISHED -j ACCEPT
# iptables -A INPUT -p tcp -m state --state ESTABLISHED -j ACCEPT
# iptables -A INPUT -p udp -m state --state ESTABLISHED -j ACCEPT
# iptables -A INPUT -p icmp -m state --state ESTABLISHED -j ACCEPT