In the latest firmware revisions for Vigor Routers, the IPSec pass-through function is disabled by default since it conflicts with the new NAT-T feature.
Cisco VPN3002 creates a VPN connection to a Cisco Concentrator at a remote location on the internet. IKE packets are going in & out of the VPN3002, but IPSec packets are not passing through the Vigor2800 router.
To allow VPN pass-through on the DrayTek router, you will need to carry the steps described below in the router configuration:
Telnet to the router and add the following command:
“‘srv nat ipsecpass on’.
To view the IPSec pass-through status enter the following command:
“srv nat ipsecpass status”