Re: VPN will not work

Jim Prendergast wrote:
Hi

All i did was update the patches on the server then it all stopped???


I have port 1723 open on the router and pointed directlt to the server via NAT

Is therre another port???


As it happens...

It's not a port, it's another protocol. It's number 47, called GRE. Most
router manufacturers don't like to mention protocols in their firewall
configurations, possibly from experience. Some routers have something
labelled PPTP which opens TCP/1723 and GRE, some silently forward GRE
when 1723 is forwarded, some forward it if you incorrectly ask for port
47 (which is an obscure FTP protocol). It all adds to the confusion.

If it was working before, then your router does one of these things,
and you don't need to worry about it separately. If you ever need to
solve something like this with a network analyser, then you need to
look for this protocol as well as TCP/1723. It is GRE which actually
carries the encrypted VPN data, while the TCP/1723 connection does
the authentication and encryption negotiation. The first thing to
travel through the tunnel is the logon information, so if the
connection appears to be made but times out on the logon, the TCP
channel is working but GRE isn't. Error 800 means 1723 isn't getting
through either.
.

Relevant Pages

  • RE: VPN to SBS through Comcast router
    ... The only thing I can find is to open TCP/UDP port 47 ... "What's GRE?". ... >> workaround for the hardware router which is not supporting PPTP connection. ... GRE is a client protocol of IP ...
    (microsoft.public.windows.server.sbs)
  • Re: VPN will not work
    ... UDP over IP = UDP/IP (IP protocol 17) ... A PPTP VPN establishes communication by calling into TCP/IPport ... 1723 but the actual VPN traffic is carried over protocol 47, GRE. ... I have port 1723 open on the router and pointed directlt to the server ...
    (microsoft.public.windows.server.sbs)
  • Re: Error 720 connecting to server via VPN
    ... Actually I've just tired that firewall rules and it didn't work. ... VPN client is not configured to allow Generic Routing Encapsulation (GRE) ... Should I setup a firewall rules to allow port 47? ... Port 1723 is allowed in my router for any WAN users to the server. ...
    (microsoft.public.windows.server.sbs)
  • Re: Adding a remote client computer to VPN
    ... I assume that the GRE 47 IP protocol is TCP not UDP? ... I would also assume that this router isn't passing GRE through in any case. ... as allegedly some routers do open protocol 47 when asked for TCP port 47. ...
    (microsoft.public.windows.server.sbs)
  • Re: PPTP through NAT device
    ... Keep in mind you need both TCP Port 1723 open and the router must pass GRE ... fact pass GRE Protocol 47 traffic. ... If you can't get PPTP VPN to work through your current router you might... ...
    (microsoft.public.windowsxp.network_web)
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