win2k VPN Error 721

[Ben]

Hello,

Strange problem, any ideas are most appreciated:

I have a Win2k Server sp4 in standalone mode running Routing and
Remote Access. I have about 10 users that are able to connect to the
server and check email and download files from our NT4.0 domain. At
remote office A i have 2 win2k sp4 clients that are able to connect
just fine. At remote office B I have 3 Win XP Pro machines that
connect fine. But I also have a Win2k sp4 machine that can not
connect. When I try to connect it gets to "Verifying user name and
password" and then throws error 721 and says the remote computer is
not responding. I don't get anything in the error logs on the server.
I am using the exact VPN client settings that work on my other
clients and am connecting with a "good" username/password. I don't
think the firewall is the problem because everything works with other
clients. I can ping the RRAS server with the client machine and I can
also open up a Terminal Server Connection to the server with the
client, just no VPN connection.

Thank you in advance for any help or ideas as to what could be the
issue.

 

[Sharoon Shetty K [MSFT]]

This error 721 is usually caused if GRE (Generic Routing Encapsulation)
protocol is blocked. The encrypted VPN data is embedded in an IP packet with
a GRE header. If anything blocks GRE , there will not be any data flow and
the connection fails.

Ports for VPN
PPTP - TCP port 1723 and IP Protocol 47 (GRE)
L2TP - UDP 500 and UDP 1701

Thanks,
Sharoon

 

[George]

I have a similar issue, Inside the LAN I can connect a VPN via PPTP
with the following; Win2k pro sp4, Win2k adv. server sp4 and XP pro
sp1. Howerver, form the internet I can not connect the XP pro sp1
client. I ge the same verifying user name and password and then error
721. Ruled out the fire wall, lost from here. In addition, it was
looking like this only appled to XP pro sp1, but I guess not. Let me
know if you hear anything on this.

Thanks

George

 

[Bill Grant]

See KB 810839 "VPN Client Cannot Establish a Connection After You Install a
Service Pack".