L2TP IPSEC VPN problem with Clients

[Guest]

HI we found a serious phenomenon with a MS VPN Server in Clients on W2k and XP.

The first one is, that we found out when the VPN connection is broken, so
the Server sends UDP packets to the CLient on port 4500. Also a Client, after
the connection is broken, he cannot reconnect. The reason is, that the VPN
CLient tries directli to open a connection on Port 4500. Due to the Server is
running on NAT, where it is necessary that the Client begins the
communication with Port 500, the Client will get a Timeout until they
rebooted. Also the Client is sending packets on port 4500 permanently after
the connection is broken. I think the Problem is the IPSEC service, on Client
and Server, because after I restarted the Ipsec-Service all senless packets
on Port 4500 stopped, but it is not a clean solution.... Does anyone have
experience with this problem?

Thanks in Advance

 

[Louise Bowman [MSFT]]

Rocco,

There are some know issues with VPN and NAT. For more info. see the article
at the following link:
http://support.microsoft.com/default.aspx?scid=kb;en-us;818043

Is the VPN server behind the NAT a Windows 2003? Is there NLB or a Cluster
in this scenario?
How is the VPN connection broken, is it the server that breaks the
connection?
Normally ipsec connections would timeout after 5-6 minutes and a new
connection using UDP 500 would be initiated. Can you confirm that even
after 6 minutes the client still attempts 4500 connections.


Louise
MSFT

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