Unable to connect to VPN using TCP protocol

[kkgadu66]

I'm working on CentOS 4.5 virtual image on Windows XP host OS. From inside the image, I can connect to VPN (with my .pcf file) using a Cisco VPN client for Linux. By default, in my pcf file the value for TunnelingMode is 0 (which means it's a UDP based connection).

The problem with UDP is that the VPN connection is terminated every 2 mins with the message "Remote peer is no longer responding". I have to reconnect again. Sometimes, I'm even maintaining a ping session (after the VPN is connected), so that the VPN connection is not terminated. But even this doesn't work.

So I changed the TunnelingMode=1 (which is for TCP), I get the following message on connecting to VPN

$ vpnclinet connect

"Secure VPN Connection terminated locally by the Client
Reason: Remote peer is no longer responding.
Disconnecting the VPN connection"

Can any one let me know why a TCP VPN connection is failing in Linux

Note: I can connect to VPN with TCP enabled on my Host OS (Windows XP). The problem is only with Linux (rather CentOS)

Thanks in advance,
Krishna