VPN Error 721

Posted on 2006-05-05
Last Modified: 2010-08-05
Hi All

I know this has been asked before, but i have looked through pretty much all of the answers in EE relating to VPN error 721.

I have an xp pro sp2 client trying to connect to an SBS 2003 sp1 server (premium, has ISA installed).

I have a speedtouch 530 ADSL modem/router with the latest firmware, which is supposed to support pptp pass through, however i cant find anywhere how to enable/disable the pptp passthrough. The sever has opened the ports required on the router for VPN, and the XP client can get as far as verifying username and password.

I believe the error message has something to do with gre 47 (general routing encapsulation) TCP port 47 (which is open).

I have just upgraded ISA to ISA 2004, and am not overly familiar to its layout yet, but browsing through the settings for VPN connection, everything seems as it should be.

I have tried enabling/disabling the ISA client on the XP machine but it makes no difference. The XP Machine has not been connected to the server since the ISA upgrade to 2004, so this could be one issue?

What sort of things should i be looking at to solve this issue?

Question by:gavinandrewmcmillan
    LVL 74

    Accepted Solution


    GRE Protocol is NOT a TCP port.  You don't need 47 open.  What you DO need is to enable GRE Protocol, which apparently can't be done through the router's interface.  Please see the SpeedTouch's user manual on how to do this through a console connection:

    LVL 2

    Author Comment

    Thanks Jeff!!

    All is good now.

    for clarification, i used telnet to go into the router, and set a new Nat entry for GRE 47.

    LVL 74

    Expert Comment

    by:Jeffrey Kane - TechSoEasy


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