I have three computers that have been accessing a site using VPN-Client. The network administrator enabled NAT-T and although a VPN connection was established, none of the remote computers could be accessed through the VPN.
Since no one else was having a problem and the vpn profile worked from other sites, it was assumed there was a problem with the router at my site. NAT-T was turned off and the remote computers could be accessed. NAT-T was turned on and the problem returned. One of the computers was no longer able to connect to the VPN at this point. The others connected but could not access remote computers.
A problem with NAT-T was listed for the LinkSys BEFSR81 version 1 router on my side. I have a DLINK D624M and switched to it. Now, the problem is even stranger.
My main computer connects through the router with no problem and I can access the remote computers. It has a fixed IP.
The second computer is a Toshiba notebook. It has the same VPN client and Windows XP Pro as the first but it cannot access the remote computers even though the VPN connection is made. It has an IP assigned by DHCP and is making a wireless connection. Disabling the firewall makes no difference. However, connecting directly through the cable modem allows the connection to work properly.
The third computer is a Gateway notebook running Vista Ultimate with the 5.0.00.0320 Cisco VPN Beta. It originally had the same behavior as the other two computers but now is unable to connect to the VPN through the router. It does not seem to see the router and fails with:
Secure VPN Connection terminated locally by the Client. Reason 412: The remote peer is no longer responding.
However, it also will connect to the VPN and remote computers when it is connected directly via the cable modem.
The router has been upgraded to the latest firmware. I am not really sure when the problem went away in the computer which works through the router since I didn't check each computer as changes were made.