Can you explain what the TCP port 1723 is? Is that negotiation part of the 
standard or rfc?
Thanks


At 05:13 PM 3/23/2002 +1030, Ben Nagy wrote:
>Because GRE (IP Protocol 47) is a protocol, and not a TCP/UDP port, the
>PIX doesn't know how to deal with it using only port address
>translation. This is fair, since GRE contains no port information, so it
>would be difficult for the PIX to work out where to send the return
>traffic without a port to use for de-multiplexing.
>
>To make this work, you will need to have a static IP translation for
>that address.
>
>Here's what's happening: First there is some control information
>exchanged over TCP port 1723. That includes the username and password
>checking, from memory - the reason it hangs there is that as soon as
>that is finished the VPN dialer expects GRE traffic to start flowing to
>confirm the connection. All this is working fine, since PAT works for
>TCP. As soon as the first GRE packet leaves outbound, your ACL permits
>it, and passes it to NAT. NAT then completely fails to figure out how it
>can create a "regular" (IP) NAT translation with no IP addresses
>allocated to a non-PAT pool.
>
>In theory, the PIX could just add an IP translation for all GRE traffic,
>and then just fail for the _next_ IP address to try and use GRE. This is
>the way a Cisco router would handle it. I presume that they chose not to
>do it that way on purpose.
>
>Cheers,
>
>--
>Ben Nagy
>Network Security Specialist
>Mb: +61 414 411 520  PGP Key ID: 0x1A86E304
>
>
> > -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED]] On Behalf Of Jay
> > Christopherson
> > Sent: Saturday, March 23, 2002 10:41 AM
> > To: [EMAIL PROTECTED]
> > Subject: Windows to Windows VPN through PIX
> >
> >
> > Hey all-
> > New to VPN's, but competent with PIX.  I have a PIX running
> > 6.1.1, brand new.  I need to allow an internal windows host
> > to establish a VPN connection with an external Windws host.
> > All traffic goes through the PIX.
> >
> > I only have a single address, and it is on the outside
> > interface, so all internal hosts are port address translated.
> >  I am not sure if this is the cause of the problem.  I know
> > that 6.1.1 allows for port forwarding via static
> > translations, and this may be part fo the eventual solution
> > (see error below).
> >
> > I have added this to the inside access-list:
> > access-list acl_inside permit gre host 192.168.1.3 host
> > xxx.xxx.xxx.xxx
> >
> > which took care of part of the problem.  However, when I try
> > to establish the connection, the connection times out at the
> > verifying username/password stage and the pix log shows this:
> >
> > 305006: regular translation creation failed for protocol 47
> > src inside:192.168.1.3 dst outside:xxx.xxx.xxx.xxx
> >
> > I cannot seem to find a reference to this particular error on
> > google...
> >
> > Anyone?
> >
> > Thanks-
> > JC
>
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