We have BT fibre to school (expensive business version as we are in the sticks), BT fibre terminator, followed by their Router which passes IP address through. Inside that we have our router, non DHCP, behind that we have our switch and server 2003 doing DHCP. Our ISP is Demon and we have our main IP address plus some others that we have never used. Am in the process of changing our (Netgear) Router to a Draytek Vigor for performance and VPN reasons.
If I set up the Vigor to one of the spare external IPs and sit it behind the BT Router, should I be able to test the port forwarding and VPN in parallel to the running system? Otherwise I have no downtime now to play with it.

Once the Vigor is up and running it supports secondary IP, so I can use the different external IP addresses in one Router.
Thanks in advance