VPN - more
With site to site and remote IPsec successfully tested, I tested L2TP. The neat thing about L2TP VPNs is client software is included in many devices, including smart phones, tablets, Windows and Apple PCs. I successfully tested L2TP connections to the ZyWALL 110 from an iPhone 4 and a Windows 8 PC.
I struggled a bit with the ZyWALL manual on how to configure L2TP, so I poked around on the web and found this forum entry that helped me out. Essentially, you configure user names, establish an L2TP address pool for remote clients, create VPN Gateway and VPN Connection settings, then enable the L2TP server on the ZyWALL and create appropriate Firewall rules. Below are screenshots of my ZyWALL L2TP Gateway, Connection, and L2TP server configuration pages.
L2TP is a good solution for remote access, but I prefer SSL VPN connections for PCs. With SSL VPNs, remote clients use a browser to establish a remote VPN connection. Software and configurations are applied to the PC automatically once the end user authenticates through the browser.
I found configuring SSL access on the ZyWALL 110 easier than IPsec and L2TP. SSL VPN configurations only require creating user names, setting up an SSL VPN address pool for remote clients, establishing an SSL VPN access policy, and entering Firewall rules. Below are screenshots of my ZyWALL SSL address pool and access policy.
SSL Address Pool
SSL Access Policy
The SSL VPN software installed on the PC is ZyWALL's SecuExtender. The ZyWALL 110 manual states SSL VPN is only supported on Windows 7, Vista, 2003, and XP. I had no problem establishing an SSL VPN connection from a Windows 7 PC to the ZyWALL 110. Below is a screenshot of the window that pops up on your PC once your SSL VPN connection is established. However, I tried setting up an SSL VPN connection on a Windows 8 PC and got a message that SecuExtender isn't supported on this version of Windows.
Updated 1/22/14: Windows 8 SSL works
ZyXEL has released SecuExtender 3.0, which I confirmed works with Windows 8.1. Download the installer and instructions from ZyXEL's French FTP site.