Re: Eigrp Query Scope

Hi Petr,

  Awesome ..Thank you very much

Regards
Anantha Subramaian Natarajan

On Sun, Aug 2, 2009 at 5:14 PM, Petr Lapukhov
<petr_at_internetworkexpert.com>wrote:

> Correction to statement (2) above - the "next-hop" may be missing the
> exact network due to filtering, not summarization.
>
>
> 2009/8/2 Petr Lapukhov <petr_at_internetworkexpert.com>:
> > Hi Everyone,
> >
> > Here is a short list of the things that limit query scoping. In short,
> > query is stopped every time the "exact" route is not found in the
> > topology table. Here is a list of the things that may cause this:
> >
> > 1) Network summarization. The query will be stopped at the "next-hop"
> > router, as that one will not have an exact match after summarization.
> > 2) Distribute-list filtering. Queries are not affected by distribute
> > lists, but will effectively get stopped if the "next-hop" router will
> > not have the network in question after summarization.
> > 3) Stub routers. Well-know scalability feature - stubs do not allow
> > for transit routing and greatly reduce the amount of queries.
> > 2) Different EIGRP ASes. Generally, queries stop at the AS boundaries.
> > However, if redistribution is configured between the two ASes, things
> > may become more complicated.
> >
> > Look at the following "diagram" with R1 being on the boundary b/w AS1 and
> AS2:
> >
> > AS1---R1---AS2
> >
> > Imagine R1 is doing mutual redistribution between AS1 and AS2 and a
> > query from AS1 reaches R1. If R1 has no ways to reach the network in
> > question, it will send a reply and remove the network from the routing
> > table. This, in turn, will make AS2 process go active (since the
> > prefix is redistributed) for the SAME network and make R1 initiate
> > another queury (leaked query) into AS2. The queury will propage AS2
> > using the regular rules. If somehow the network will be found, R1 will
> > update the routing table and may re-inject the prefix into AS1.
> >
> > As for the new query scope in AS2, it may be one hop or more,
> > depending on the filtering/summarization configuration and/or the
> > number of mutual redistribution points between AS1 and AS2. In optimal
> > case, if you are using route summariztion and dont have multiple
> > redistribution points, the leaked query will travel just one hop deep
> > into AS2.

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Received on Sun Aug 02 2009 - 17:16:36 ART