IPtables is the default firewall on Redhat-based distros.

http://www.cyberciti.biz/faq/rhel-fedorta-linux-iptables-firewall-configuration-tutorial/

1. Set the default policies for each of the built-in chains to ACCEPT
2. Flush the nat and mangle tables
3. Flush all chains (-F)
4. Delete all non-default chains (-X)

iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
iptables -t nat -F
iptables -t mangle -F
iptables -F
iptables -X