Reference Manual

NAME

gmap - maintain the GRE mapping table

gmap [add|delete PrivateIP PublicIP]

Command gmap is used to add or delete mappings for GRE packets (protocol 47) used by the PPTP protocol in products such as Microsoft's Virtual Private Networking.

Gmap with no arguments prints the current mappings.

PrivateIP is the IP address of the private end of a VPN connection, PublicIP is the IP address of the Internet end of a VPN connection.

Only one VPN connection at a time from any private machine to any VPN server may be established. Up to 64 private machines may establish a VPN connection to any VPN server.

If the VPN server allows Internet access, a private machine may use a VPN connection to obtain a new IP address. This allows NAT-hostile applications to run normally on that private machine.

Note that the same mapping table is used for IPsec (protocols 50 and 51), IP over IP (protocol 97) and L2TP (protocol 115) packets.