If it's a production box, get professional help. Anything you copy/paste from the net without understanding could jeopardise your system.
The most likely firewall would be iptables based. To check if there are any rules configured for the various tables, use the following bash
for command as root. The output below the command shows no rules and default policy of ACCEPT, meaning nothing is being blocked and the firewall is effectively disabled.
Code:
user@host:~$ for TABLE in filter nat mangle raw; do echo "Listing table data for: $TABLE"; iptables -t $TABLE -L; echo " "; done
Listing table data for: filter
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Listing table data for: nat
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Listing table data for: mangle
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
Listing table data for: raw
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Any iptables output other than what you see above, except for an error, likely means that there are some kind of firewall rules in place.