leave the vpn window open, and see whether you can browse other website.

Regarding iptable, there are a lot of tutorials or documents online. Or you can just man "iptables".

If you just want to disable it, use the command in /etc/init.d, should be something like "/etc/init.d/iptables stop" . Do not just flush the chain because you will have a number of chains to flush.

To verify the firewall rules, "iptables -L" . If the output shows the policy is ACCEPT and there is no rules, that means the firewall is not blocking anything.