Troubleshooting firewall issues
Windows XP and SuSE Linux have firewall systems installed that are activated automatically after installation. Like most (personal or desktop) firewalls, these are configured to allow traffic originating from the local system and destined for the Internet or the local network. This configuration is sufficient for OpenVPN in almost every case. However, if your tunnels won't start and you receive messages announcing connection problems, it may be the fault of a misconfigured desktop firewall. As only SuSE Linux and Windows XP come with preinstalled firewalls which may conflict with OpenVPN, we will learn how to quickly deactivate them for testing purposes.
Deactivating the Windows XP service pack 2 firewall
On Windows ...