Subject: L2F / L2TP Questions

From: John Narron <[email-masked]>
Date: Thu, 9 Nov 2000 10:50:09 -0600 (CST)

Greetings all,
    We're about to embark on some expansion using some L2F/L2TP
wizardry, and well frankly I'm not to sure how to set this crap
up.  We got the frame-relay circuit between the two access points
set up correctly, but there's a slight problem - the LAC uses
L2F, and the LNS only does L2TP.  I had thought L2TP was backwards
compatible w/ L2F?  Am I right, or was I smoking some bad stuff?
If it is right, how would one go about getting the authentication
of the tunnels working as well?  Generic instructions would be
useful, but if anyone knows how to set up an LNS on a Portmaster 3
(from Livingston/Lucent) it would be a major help.

  Thanks,
     John

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From: Ignacio Goyret <[email-masked]>
Date: Thu, 09 Nov 2000 15:11:13 -0800

At 05:00 PM 11/9/00 -0500, James Carlson wrote:
>John Narron writes:
>No, that's not right.  L2TP can *coexist* with L2F on a given system
>because they use different GRE version numbers, but they're in no way
>compatible with each other.

That's not quite right either :-) Neither L2F nor L2TP use GRE.

L2F and L2TP share UDP port 1701. Since the size and position of the
version field in the headers were made to match, you can distinguish
one from the other.

However, they are incompatible one with the other. They have different
encodings, options, etc. Read RFC 2661 (L2TP) and RFC 2341 (L2F) for
further information.

---

From: James Carlson <[email-masked]>
Date: Thu, 9 Nov 2000 17:00:16 -0500 (EST)

-- 
James Carlson                                  <[email-masked]>
"PPP Design and Debugging" --- http://people.ne.mediaone.net/carlson/ppp