All Barracuda SSL VPN units, all versions.
Answer:IPSEC configuration on MS Windows Vista/7/2008 and XP:
There is potentially needed registry change that will be needed, assuming everything else has been verified with the appropriate ports opened on the Firewall forwarded to the SSLVPN (ie, 4500 NAT-T,500 ISAKMP) TCP/UDP
By default, Windows Vista and the Windows Server 2008 operating system do not support Internet Protocol security (IPsec) network address translation (NAT) Traversal (NAT-T) security associations to servers that are located behind a NAT device. Therefore, if the virtual private network (VPN) server is behind a NAT device, a Windows Vista-based VPN client computer or a Windows Server 2008-based VPN client computer cannot make a Layer Two Tunneling Protocol (L2TP)/IPsec connection to the VPN server. This scenario includes VPN servers that are running Windows Server 2008 and Microsoft Windows Server 2003.
Because of the way in which NAT devices translate network traffic, you may experience unexpected results when you put a server behind a NAT device and then use an IPsec NAT-T environment. Therefore, if you must have IPsec for communication, we recommend that you use public IP addresses for all servers that you can connect to from the Internet. However, if you have to put a server behind a NAT device and then use an IPsec NAT-T environment, you can enable communication by changing a registry value on the VPN client computer and the VPN server by using the following article:
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