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PPTP Outbound

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PPTP Outbound - 8.Apr.2005 10:03:00 PM   


Posts: 1
Joined: 4.Mar.2004
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Does anyone know if ISA Server 2004 supports outbound PPTP vpn passthru. I have a client with an ISA Server 2004. They need to have internal computers connect via PPTP to their remote sites. It works fine with ISA 2000, but I can't get it to work with 2004.
Post #: 1
RE: PPTP Outbound - 8.Apr.2005 11:01:00 PM   


Posts: 12830
Joined: 1.Jun.2001
From: Belgium
Status: offline
Hi TRB3,

check out http://support.microsoft.com/?scid=kb;en-us;838245 .


(in reply to tblandford)
Post #: 2
RE: PPTP Outbound - 10.May2005 6:29:00 AM   
I have set up the access rules according to the KB article, but outbound PPTP isn't working.
The ISA Server 2004 log shows the action "Initiated Connection" to 1723 on Protocol PPTP. The Windes XP VPN client is never able to make a connection and times out.
I am using Windows XP as a SecureNAT client without the ISA Server client software.
The tech guy on the other end says that his VPN is reporting bad packets. They usually use the Windows XP VPN client to connect to their VPN. This is the 2nd system that I haven't been able to connect to when using PPTP through ISA Server 2004. I haven't had it working yet.

Anybody have any ideas on what could be wrong? Or what the next steps are to troubleshoot a problem like this?


(in reply to tblandford)
  Post #: 3
RE: PPTP Outbound - 10.May2005 6:42:00 AM   
Does the outbound PPTP problem I am having have anything to do with Route vs NAT in "Network Rules"?
It does appear that an initial connection is made to the external PPTP server I am trying to connect to or the ISA Server 2004 log would have shown a failure instead of "Initiated Connection". But that is as far as I can tell the PPTP session attempt goes before the timeout failure occurs.
I think that the network rule that currently applies to my connection attempt is "Internet Access" which has NAT for the Relation property.


(in reply to tblandford)
  Post #: 4
RE: PPTP Outbound - 13.May2005 4:50:00 PM   
I am having the same problem and it looks like i have the same topology as yourself. Any ideas would be greatly appreciated.

I thought it could be to do with the fact that both my router and ISA firewall were carrying out Network Address Translation so i set up the ISA 2004 firewall to route traffic between the networks, leaving the NAT to the router.

Interestly enough i can connect to remote pptp vpns where the vpn server is acutally on a public ip, but if the remote vpn server is behind a router which port forwards pptp then i cannot connect.

I didn't have this problem when i ran our network with purely the adsl router, with it's own firewall, so i know it's not a pptp pass-through problem on the router.


(in reply to tblandford)
  Post #: 5
RE: PPTP Outbound - 25.May2005 6:36:00 PM   
There was a bug introduced in a recent Windows XP update and Server 2003 SP1 which can cause VPN and RDP to fail. I wonder if that is what the problem is?


(in reply to tblandford)
  Post #: 6
RE: PPTP Outbound - 26.May2005 5:14:00 PM   


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Joined: 24.Aug.2004
Status: offline
I have the same problem here.
In logging, i see initiated connection, but vpn pptp connection from client to external vpn pptp server won't work. I also used the standard pptp protocol in isa 2004. In the standard protocol, only tcp port 1723 is used, is this enough ? i read something about port 47 ?

(in reply to tblandford)
Post #: 7
RE: PPTP Outbound - 29.May2005 12:57:00 AM   


Posts: 420
Joined: 27.Apr.2005
Status: offline
Have you tried setting up Allow All protocol Access Rule? Does PPTP still fail?

(in reply to tblandford)
Post #: 8

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