VPN stopped working after two years!

[amillsmcewan]

Hello

I'm hoping that the experts browsing this forum can help, I'm going nuts with this problem...

I use a VPN connection from my laptop (working at my client) to my home office. All worked well for the last two years until a few weeks ago. To my knowledge I have changed nothing.

Details:

Windows XP home SP2 on both machines. D-Link router at home office with VPN pass-through enabled and relevant port forwarding for PPTP and IPSec. Windows firewall disabled on both laptop and VPN Server machine. Norton anti-worm disabled on both machines.

Error message is VPN Error 721. I have also tried to use VPN connection from laptop while at home with the same error, so it's presumably nothing to do with my client's firewall or anything.

I can access the home office computer using Ultra VNC with no problem.

Thank you in anticipation for your help!

Alastair

[johnwill]

What specific VPN client are you using? Have you tried disabling any firewalls at the home office for a test?

[amillsmcewan]

John

Thank you for your reply. I am using the standard VPN client provided with Windows XP Home. Windows firewall is disabled on both client and server machines. I've also tried disabling anti-worm protection on both machines with no effect.

[StressedTechie]

Your Norton Security Software on your laptop hasnt got its firewall on has it! I had this the other day had me stumped for ages Windows Firewall was off but couldnt connect for love nor money! Then i checked Norton and its firewall was on!! I turned it off temporarily and then I could connect!! Worth checking mate!

ST

[amillsmcewan]

Hello ST

Thanks for your post. I don't have Norton Personal Firewall installed just antivirus. The thing that previously interfered with VPN when I set it up 2 years ago was the anti-worm protection in Norton Antivirus. I turned that off 2 yrs ago and all was well. Something must have changed recently but I simply can't think what!

Alastair

[StressedTechie]

hmm!
Let me do some research quick!

[StressedTechie]

Hi amils...

Just googled the error and Miccrosft has a Technical Paper on it
http://support.microsoft.com/kb/888201
see if that helps. Either way let me know how you get on!

[amillsmcewan]

Hi ST

Thank you for the reference to the MS paper. I have double checked my D-link router and all I can say is that the system setting "VPN Pass through" is still set to "enabled" for both PPTP and IPSec.

The firewall settings (which are created automatically when PTP and IPsec are specified in the virtual server configuration of the router) are set to allow PPTP traffice on port 1723. My understanding is that it's the "VPN-pass through" setting that permits GRE protocol 47. So, so far as I'm aware, all seems to be consistent with what MS say in the paper. Very frustrating!

Regards

Alastair

[StressedTechie]

Hi Alastair this problem has me intrigued.

Anyway I have found numerous articles but all seem to be suggesting the 721 error is relating to the GRE Protocal 47.

One suggestion on another site was to clear the checkboxes for PPTP and IPSec passthrough on your router, Hit...submit/apply/change, then enter the checks again, and submit/apply/change. And try again! I doubt it will as easy as this but it may be worth checking.

After that the suggestions are along the lines of hitting reset on the router returning it to Factory default settings and resetting up!!

[amillsmcewan]

Hello ST

I'm sure that I would be in a more resourceful state of mind if I could be "intrigued" rather than frustrated! I need to practice!

I'll give your idea a try and report back after the weekend. Many thanks for your interest in this.

Alastair

[amillsmcewan]

Well I checked the D-link firmware was the latest version (it is) and reset to factory defaults, adding back in the port forwarding entries. Unfortunately no change. Bittorrent works fine, UltraVNC works fine but VPN still gives error 721. I deleted the inbouind netwrok connection on the server and the outbound VPN connection on the lcient, and added them back in again using the wizard...no change. Time for a drink!

[StressedTechie]

Hi Alastair
Must admit my intrigue is now turning to frustration!

What is the actual message your getting!
Is it
Error 721: Remote PPP peer is not responding

If so this issue may occur if the PPTP server replies by using an Internet Protocol (IP) address that is different from the address that the PPTP client computer sent the request to. This issue may occur if either one of the following conditions is true:• The server has multiple IP addresses on the public network interface.
• The server is multihomed, and the configuration of the default gateway is on the incorrect interface.
The PPTP client detects the change in the IP address between the request and the reply. Therefore, the client does not permit the connection to be completed when the other IP address in the reply from the PPTP server is used.

The article is as follows
http://support.microsoft.com/kb/271731/en-us

let me know if this helps!

[amillsmcewan]

Hello

The actual message is just Error 721 - Cannot Connect to the Remote Computer.

I did read the MS whitepaper and tried the registry change anyway but no result unfortunately.

Kind regards

Alastair

[amillsmcewan]

PS I've also tried mucking about with MTU settings to no effect

[amillsmcewan]

Dear All and especially Stressed Techie

My VPN is working. I'd like to be able to tell you how but I have changed nothing since my last post and it is now working. Sunspot activity perhaps? Sorry that there has been no blinding revelation that I can share with the people who have a similar problem.

Kind regards

Alastair

[johnwill]

Maybe something changed on the other end.

[amillsmcewan]

I think I might have an explanation of why my VPN stopped working after two years.

I now realise that the time it stopped working concided with my buying a laptop for my daughter to take to university. I set up a network connection for her to access our wireless home network until she went and I used the network connection wizard to do it. I think I must have inadvertently set up Internet Connection Sharing (ICS) for the network instead of making it access the internet via our router. I noticed the other day that other computers on our network were showing Internet Gateway as a connection, where I wasn't expecting any (since, as I said, I'd thought all the computers accessed the internet via our router. It seems that they might all have been routed via my daughters laptop instead).

I reconfigured all the computers to get rid of this and changed my daughter's laptop too. VPN from my remote laptop in ot the study computer seems fine now. I'm not technical enough to know if this is cause and effect but thought I'd post this information in case it helps anyone else.

Kind regards

Alastair

[johnwill]

Well, that would explain it!

There's always a logical reason, sometimes it takes a while to find it.