When you sign up to the High Bandwidth (Router support) package you are sent a script that you place according to this setup guide:
http://www.purevpn.com/vpn-service/router-vpn.php
5th line on the script reads:
/sbin/route add -host ********** gw ********* dev vlan1
This is a generalized script. Where you see "vlan1" - This is where you will need to make change according to your router model. Some routers have eth1, some have vlan2 so definitely if your router is ,for example, vlan2 then this script won't work unless you correct this.
In order to find correct interface name, you will need to take following steps:
1) Telnet your DD-WRT router. It will prompt for user id and pass
2) Enter your router's user id and pass. It will get you to CLI console.
3) write "route" and hit ENTER. It will bring up routing table for you.
4) Locate the "default" route and note the interface for this route. This is the interface that you need to replace with "vlan1" provided as default in script.
That's it. Reboot your router, wait for upto 5 minutes and it should fire up!
** This is for fairly technical people. So don't attempt if you don't know what's going on. Get our support staff help you set it up