PPTP VPN tunnel works via modem but not broadband, why?


B

Bo Berglund

We have a company LAN protected by a Symantec Raptor firewall.
Through this we have set up a PPTP VPN tunnel service that is handled
by an internal W2000 server.
Users connect using the standard VPN client on WinXP-Pro laptops when
they are on the road. This works fine when they use dialup access to
Internet and then connect the VPN tunnel.
They can use file shares on the servers and the Exchange server too.
They can also connect to various PC:s on the LAN using Remote Desktop.

The problem I am facig is on a home LAN (mine as a matter of fact),
where I have broadband ADSL access to Internet via a D-Link router.
If the laptop that works fine in the scenario above is connected to
this home LAN it can establish its VPN connection just fine and it has
the ability to use file shares and the Exchange server.
But strangely the Remote Desktop functionality is not available, or
rather it seems like it is discovered during RD connection because the
window comes up. But then everything stops and after a minute or so
there is a network error display.

The stranges thing is that a number of months ago this was working
just fine...

My analysis leads me to my home LAN somehow, but where?
- Modem connection to Internet menas that all VPN functions are OK.
- ADSL connectioon to Internet means that all VPN functions except
Remote Desktop works.
- The two cases above differ in one aspect only: When using ADSL the
connection to Internet is not modem but Ethernet (should be faster).

Where should I start looking?
Is there a possibility that some Windows Update stuff screwed up my
system? But then again the laptop test done just minutes ago show that
the laptop works fine over modem but not over Ethernet...

/Bo


Bo Berglund
bo.berglund(at)nospam.telia.com
 
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R

Robert L [MS-MVP]

We have seen more and more cases like this one. I would check the MTU first.

vpn drop connection The both offices can browse over the VPN without problem. ... VPN client to the Server. Resolution: modify the MTU. Related Topics. How to modify the MTU ...
www.chicagotech.net/vpnissues/vpndorp1.htm


Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on http://www.HowToNetworking.com
We have a company LAN protected by a Symantec Raptor firewall.
Through this we have set up a PPTP VPN tunnel service that is handled
by an internal W2000 server.
Users connect using the standard VPN client on WinXP-Pro laptops when
they are on the road. This works fine when they use dialup access to
Internet and then connect the VPN tunnel.
They can use file shares on the servers and the Exchange server too.
They can also connect to various PC:s on the LAN using Remote Desktop.

The problem I am facig is on a home LAN (mine as a matter of fact),
where I have broadband ADSL access to Internet via a D-Link router.
If the laptop that works fine in the scenario above is connected to
this home LAN it can establish its VPN connection just fine and it has
the ability to use file shares and the Exchange server.
But strangely the Remote Desktop functionality is not available, or
rather it seems like it is discovered during RD connection because the
window comes up. But then everything stops and after a minute or so
there is a network error display.

The stranges thing is that a number of months ago this was working
just fine...

My analysis leads me to my home LAN somehow, but where?
- Modem connection to Internet menas that all VPN functions are OK.
- ADSL connectioon to Internet means that all VPN functions except
Remote Desktop works.
- The two cases above differ in one aspect only: When using ADSL the
connection to Internet is not modem but Ethernet (should be faster).

Where should I start looking?
Is there a possibility that some Windows Update stuff screwed up my
system? But then again the laptop test done just minutes ago show that
the laptop works fine over modem but not over Ethernet...

/Bo


Bo Berglund
bo.berglund(at)nospam.telia.com
 
B

Bo Berglund

We have seen more and more cases like this one. I would check the MTU first.

vpn drop connection The both offices can browse over the VPN without problem.
... VPN client to the Server. Resolution: modify the MTU. Related Topics.
How to modify the MTU ...
www.chicagotech.net/vpnissues/vpndorp1.htm


Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on http://www.HowToNetworking.com

Thanks,
I will try this. The document link locates the registry key
erroneously, but I found it so it is OK.
Question:
Does this apply to the client or server or both?

/Bo

Bo Berglund
bo.berglund(at)nospam.telia.com
 
B

Bo Berglund

Thanks,
I will try this. The document link locates the registry key
erroneously, but I found it so it is OK.
Question:
Does this apply to the client or server or both?

Answering myself:
After lowering the MTU value to 1200 for both Protocol and Tunnel I
get immediate connection of the Remote Desktop session. :)

Thanks for the tip!


Bo Berglund
bo.berglund(at)nospam.telia.com
 
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R

Robert L [MS-MVP]

Thank you for the update. we need that.

Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on http://www.HowToNetworking.com
Thanks,
I will try this. The document link locates the registry key
erroneously, but I found it so it is OK.
Question:
Does this apply to the client or server or both?

Answering myself:
After lowering the MTU value to 1200 for both Protocol and Tunnel I
get immediate connection of the Remote Desktop session. :)

Thanks for the tip!


Bo Berglund
bo.berglund(at)nospam.telia.com
 

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