L2TP over Wireless and NAT

From: Newscene (not_real_at_internet.org)
Date: 02/25/05 

Date: 25 Feb 2005 11:08:06 -0600

I am trying to configure an L2TP/IPSec connection from my home to my office
VPN server. We have been using PPTP for VPN for some time now in the
wireless configuration with no problems; the only difference is we are
trying to move the VPN to L2TP. The client is a Thinkpad T40 (built in
802.11A/B) running Windows XP Pro (SP2) and the target is a Windows 2000
Advanced Server (SP4). The client is on a 802.11A/B WLAN using NAT on a
DLink DI-764 (with current firmware) behind a Speedstream 5260 DSL modem.
The Office LAN is on a Cisco 2620 with integrated firewall and the firewall
has the all the necessary ports and protocols enabled for both PPTP and
L2TP.

I believe the client, the server and firewall are correctly configured as I
am able to establish a L2TP connection from the Thinkpad using either a
Verizon CDMA 1xEVDO PC-5220 wireless card* or by connecting the notebook
directly to the DSL modem. However if I try L2TP using my WLAN connection
the L2TP connection returns Error 678. There is no indication in the server
logs that a VPN attempt was made. As I said, a PPTP connection establishes
instantly in this configuration and the L2TP establishes immediately outside
the WLAN so I am fairly confident the problem lies with the NAT.

The DLink has an option to allow VPN passthrough for PPTP and IPSec VPNs and
these are set. I spent several hours on the phone with DLink support trying
various combinations of settings on the DLink including: direct wired
Ethernet connection of the notebook to the router; configuring the notebook
on the router's DMZ; etc. all with the same result.

I have read the docs on Microsoft about XP and 200x support for L2TP and NAT
and I am at a loss where to go from here. If anyone has seen this problem
and has a solution I'd certainly appreciate hearing from you.

---------------
* By the way, I heartily recommend this wireless service. I am in South
Florida and we routinely achieve connections of 400KB with this service.

Relevant Pages

  • RE: VPN issue on SBS2003
    ... I understand that you encountered VPN connection issue when you use VPN to ... Internet clients or VPN to external VPN Server from SBS Client computers? ... Configure E-mail and Internet Connection Wizard ... Total GRE packets sent = 1 ...
    (microsoft.public.windows.server.sbs)
  • RE: PPTP VPN connection problems
    ... The problem is that the VPN does not disconnect. ... However after some idle period I can not send packets across the connection. ... A ping to the server would result in "Request timed out". ... If I connect with the VPN client locally to the internet ...
    (microsoft.public.windows.server.sbs)
  • Re: VPN Ports to Open
    ... the VPN connection after you change the firewall before SBS. ... On the server, please stop the Routing and Remote Access service. ... Total GRE packets sent = 1 ...
    (microsoft.public.windows.server.sbs)
  • Re: Windows 2003 VPN Default Gateway Issues
    ... Ethernet adapter Local Area Connection: ... If the VPN server is configured to use a static IP address ... the default gateway on the client is not the problem. ...
    (microsoft.public.windows.server.networking)
  • RE: VPN Connectivity issues through LAN
    ... I understand that you cannot ping SBS after ... you can establish VPN connection from the remote LAN. ... You have to rerun the CEICW to make sure your SBS 2003 server have right ...
    (microsoft.public.windows.server.sbs)
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