Finally one day (a week back), I sat down tried to break my head over it and solved it under 2 hours. Quite pleased with the effort.
Issue: Nortel VPN not connecting via wifi router (netgear in my case) but connects via LAN (directly to the modem)
What I did:
You can access your Modem's application as follows
Link - http://192.168.1.1/
Username / password - admin / password (usually but if it doesn't work search in the net for the right one)
Link - http://www.routerlogin.net
Username / password - admin / password (usually but if it doesn't work search in the net for the right one) [for the virgin media provided wifi router it is virgin/password]
For the VPN to work
Add port triggering for the following ports 50, 80, 500, 4500, 1701, 1723 under both the Wifi and modem's application.
And then Navigate to the wan setup under the wifi router's application and
check the Disable SPI Firewall.
Restart the modem and your system and connect to VPN and voila you connect and if it works drop a comment :)