[BIG FYI] if you cannot ping or access outside of server

[brianhenson]

If you cannot ping or access anything outside of the 127.0.0.1 address space run this command.

Code:

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

This must be in place to allow communication. But due to the code using iptables for traffic management and their refusal to add this rule you must do it your self. Debian by default (at least on my etch box) had a default deny rule that killed any communication not allowed by a rule. This is to fix issues with the isp_network daemon.