RE: VPN Connects once then Error 721

Hi Terry:
>From your description, I understand that when you try to establish a VPN
connection, the connection fails and you receive an error 721. If I am off
base, please feel free to let me know.

Based on my research, error 721 is usually caused by GRE packet not
properly being allowed on a router.

To verify whether the router is the root cause, please do the following
steps:

a. Please temporarily place a client directly connected to the external NIC
of the SBS Server. You can connect the external network adapter of the SBS
Server to a simple hub and connect the client to the same hub.

b. Manually configure the TCP/IP settings on the client computer to be on
the same subnet as the external network adapter of the SBS Server.

c. Turn off the Firewall Client on the client computer.

d. Configure the VPN connection on the client and do a VPN test.

Does this problem persist?

If the above test works fine, it reveals that the traffic is blocked by the
hardware router. Please double check if the router is configured to forward
the corresponding ports to the SBS box.

For your information:
Generally speaking, we need to enable TCP port 1723, as well as an
additional IP port 47 (GRE protocol) on all routers and firewalls between a
PPTP client and a PPTP server. The router must be able to pass Generic
Route Encapsulation (GRE) protocol 47 for PPTP traffic to connect correctly
to use VPN. When a cable/DSL router cannot map GRE protocol 47 to the
Routing and Remote Access server, you cannot connect to the server from the
Internet.

GRE Protocol 47 Packet Description and Use
http://support.microsoft.com/default.aspx?scid=KB;[LN];241251


If problem doesn't reside in the router side, we may need a further
investigation. Please help me collect the following information:

1. How many external Nics does your server have? If you have multiple
external adapters on your server, you should refer to this article:

PPTP clients cannot connect to a PPTP server that has multiple IP addresses
http://support.microsoft.com/default.aspx?scid=KB;EN-US;271731

2. Please re-run the CEICW Wizard in order to make sure the internet
connection is properly configured. Please refer to this KB article:

825763 How to configure Internet access in Windows Small Business Server
2003
http://support.microsoft.com/?id=825763

Then run the Configure Remote Access Wizard, follow the instructions and
finish the wizard.

3. Do you have ISA Server installed? If so, what is the version of the ISA?

4. What changes have been made to the SBS Server when the error occurred?

Hope the information helps. Please feel free to let me know if you have
further concerns. Thank you!

Have a nice day! :)

Best Regards
Edward Tian(MSFT)
Microsoft CSS Online Newsgroup Support

Get Secure! - www.microsoft.com/security
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--------------------
| Thread-Topic: VPN Connects once then Error 721
| thread-index: AcWy8mdof4VCZCZhQwyHlO20xdkjqw==
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| From: =?Utf-8?B?VGVycnlV?= <TerryU@xxxxxxxxxxxxxxxxxxxxxxxxx>
| Subject: VPN Connects once then Error 721
| Date: Tue, 6 Sep 2005 07:51:03 -0700
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|
| I have set up a SBS 2003 for a client and want remote branches to use
VPN.
| The SB VPN Server sits behind a Vigor 2600G router using ADSL. Initially
I
| manually setup a Win XP VPN Client to the main IP of the router and
| sucessfully connected and authenticated. I then set up a CMAK package to
| access the SBS using an alias static IP and also connected succesfully
and
| used the connection for about five hours. However when I tried to
connect
| the next day it came back (eventually) with a 721 error. I then tried my
| original connection and that had same problem. After numerous
unsuccessful
| tries, I set a different main IP on the router and modified the IP on the
| manual connection and straight in. Disconnected and then tried to
reconnect
| and error 721. ?????? Any suggestions. Thought about IP Protocol 47 but
| according to Draytek when Port 1723 is opened it automatically sets the
| appropriate IP Protocol. Be very grateful for assistance
|

.

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