after connection completed thru ISP, still cant ping internal network.

Here's the situation:
when trying to start VPN login when connected with a laptop while
attached to the internal network, it al works fine. Once outside the office,
making an connection through an ISP, I can connect to the VPN server while
unchecking netware login.
When selecting netware login I get 'tree or server could not be

When connecting to VPN server thru ISP, I can't ping the private or
public adres of the vpn server.

please help