This describes VPN support by model. Depending on your ISP configuration and other issues, you may need to open ports for passthrough to work. These ports are:

• IPSec: 500
• L2TP: 1701 and 500
• PPTP: 1723 and 500

VPN Passthrough

• Each VPN passthrough must have its own 500 port open. The first port is opened normally, as described in port forwarding documents. The other instances of port 500 must each be opened by selecting a unique range of ports that include 500, e.g., 499-501, 498-502, etc.
• "VPN passthrough Connections" is the total tunnels of all types supported. For example, the first model, CG814M, supports 1 IPSec or L2TP or PPTP passthrough, not three.
• See VPN Passthrough Connections Limited by Network Configuration to understand how network configuration can limit number of VPN passthrough connections to fewer than the maximum which is listed here.

Doc: N101222.asp Jan. 19, 2004