According to SAFE implementation of IPSec VPN, what is the function of a VPN router in a large network remote access and VPN module?

A.
Authenticates individual remote users using XAUTH and terminates their IPSec tunnels.

B.
Tracks the availability of remote site networks across the VPN routers.

C.
Authenticates trusted remote sites and provides connectivity using GRE/IPSec tunnels.

D.
Authenticates trusted remote sites and provides stateful filtering of remote site traffic.