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Connecting to Windows VPN Server

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Connecting to Windows VPN Server

Has anyone come across a really weird problem when connecting to a windows VPN server from a PC running W2K or XP. The PC establishes a connection, traffic flows fine between the PC and VPN server, but after about 20 seconds all activity stops. Then about 10 seconds after that the VPN connection hangs up.

Any ideas or suggestions would be most welcome.

Will
8 REPLIES
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Connecting to Windows VPN Server

Are you running a firewall? hardward or software based? sometimes they can close ports if they suspect an attack.

Do you have a router? if so, have you checked the logs?
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Connecting to Windows VPN Server

I'm on a laptop using a software firewall. (Norton internet security) If I connect the laptop up to a different ADSL line provided by someone other than PlusNet, the connection works fine. PlusNet say they are not blocking or dropping any ports although if it works with other ISP's then I can only assume it's something to do with them.

Any Ideas?
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Connecting to Windows VPN Server

Once the VPN has dropped, attempt to ping a few sites. What results do you get?
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Connecting to Windows VPN Server

Plus Net to my knowledge only block port 135, see topic below

http://portal.plus.net/central/forums/viewtopic.php?t=15628

Have you tweaked your mtu or any other settings, as this can affect VPN connections?

when you say, you've tested it against other ADSL lines, how? Are these friends who have different ADSL connections?

Are you using a USB modem or Ethernet based modem or router for your connection?
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Connecting to Windows VPN Server

If I setup a continuous ping, no packets are lost during the drop out of the VPN. Even if that ping is directed at the IP address of the VPN server.

I’ve tested the VPN by plugging my modem in to an ADSL line provide by BT open world. My modem is a standard DM602 Netgear and it happens if I use the USB port and Ethernet port.

I haven’t touched my MTU settings.

I am running the external IP over a NAT in order to us the PAT functions on the router. Could that cause drop outs?
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Connecting to Windows VPN Server

The pings where to rule out the 135 port block. If it was this, the ping flow would have stopped. Rulled that one out.

Next.

What does the remote side on the connection report in the logs?

This is just as important, if not more, than prooving it isn't your side.
mssystems
Rising Star
Posts: 269
Thanks: 33
Fixes: 1
Registered: 10-08-2007

Connecting to Windows VPN Server

Quote
I am running the external IP over a NAT in order to us the PAT functions on the router. Could that cause drop outs?


NAT can cause problems with VPN connections, but it is more usual that the VPN completely fails to connect.

If your using the same modem on the non-plus.net line it should rule the modem out. Having said that if the line quality is substantially lower on the Plus.net line, the modem may still cause problems.

A couple of pointers:
Check the event log on both your XP system and the server. The disconnection event may indicate if the call cleared normaly and from which end it was cleared.

Do a tracert from the Plus line and the Openworld line. Are there any significant differences in the latency?

BTW: what type of VPN is it PPTP or IPsec

Regards
Matt
www.mssystems.co.uk
mssystems
Rising Star
Posts: 269
Thanks: 33
Fixes: 1
Registered: 10-08-2007

Connecting to Windows VPN Server

Quote
I am running the external IP over a NAT in order to us the PAT functions on the router. Could that cause drop outs?


NAT can cause problems with VPN connections, but it is more usual that the VPN completely fails to connect.

If your using the same modem on the non-plus.net line it should rule the modem out. Having said that if the line quality is substantially lower on the Plus.net line, the modem may still cause problems.

A couple of pointers:
Check the event log on both your XP system and the server. The disconnection event may indicate if the call cleared normaly and from which end it was cleared.

Do a tracert from the Plus line and the Openworld line. Are there any significant differences in the latency?

Make sure you have the latest firmware on the modem.

Turn off the Norton firewall for testing purposed.

BTW: what type of VPN is it PPTP or IPsec

Regards
Matt
www.mssystems.co.uk