[cisco-bba] Multilink PPP over L2TP

Oliver Boehmer (oboehmer) oboehmer at cisco.com
Tue Mar 2 02:03:30 EST 2004

Hi Ash,

> Guys, I have tested this variety of multilink and connectivity seem
> to be fine. However I have a few questions:
> 1) Each session in the MLP bundle is given a virtual access
> interface. What do the counters of this interface hold?

what do you mean specifically? the multilink bundle interface (MLP
bundle) sees IP packets, the individual member links only see the
(possibly fragmented) MLP L2 packets (including PPP keepalives, etc.)

> 2) Each ppp session is authenticated against the radius server when
> it comes up. How can you get the router to send multilink attributes
> (or something similar) to the RADIUS server so that it does not
> allocate more dynamic IP address from its local pool which don't get
> used? 

Unfortunately this is not possible. By the time the link is
authenticated, IOS doesn't know yet if this is part of a multilink
bundle. Forwarding a link (to join a multilink bundle, possibly on
another LNS via multi-chassis multilink-ppp) happens after
authentication phase.

You can process the accounting packet (using the non-standard
"Ascend-Num-In-Multilink" attribute 188) to see if this link is the
first or a subsequent link in a bundle.


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