Subject: [Isis-wg] Summary Address

From: "Purushothaman NandaKumaran" <[email-masked]>
Date: 6 Jun 2001 07:42:46 -0000

Hi,
I have some doubts in advertising summary routes.

1) Whether the configured summary address will go as IP internal or external reachability information in the generated LSP's?

2) If some redistributed routes fall under the summary route (redistributed routes will be sent as IP external reachability information) and if some level 1 routes also
fall under the same summary route (level 1 to level 2 which should go as IP internal reachability information)
then how should we advertise that summary route?

Please clarify my doubts.
thanks in advance,
Purush

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From: Henk Smit <[email-masked]>
Date: Wed, 6 Jun 2001 15:25:42 -0700 (PDT)

> 1) Whether the configured summary address will go as IP internal or
>     external reachability information in the generated LSP's?

  Not defined anywhere, AFAIK.

> 2) If some redistributed routes fall under the summary route
>     (redistributed routes will be sent as IP external reachability
>     information) and if some level 1 routes also > fall under the same
>     summary route (level 1 to level 2 which should go as IP internal
>     reachability information) > then how should we advertise that summary
>     route?

  Not defined anywhere, AFAIK.

> Please clarify my doubts.

  See RFC1195.
 We quote the relevant section in rfc2966.

   RFC 1195 states this quite clearly in the note in paragraph 3.10.2,
   item 2c).  This document does not alter this rule of preference.

       NOTE: Internal routes (routes to destinations announced in the
       "IP Internal Reachability Information" field), and external
       routes using internal metrics (routes to destinations announced
       in the "IP External Reachability Information" field, with a
       metric of type "internal") are treated identically for the
       purpose of the order of preference of routes, and the Dijkstra
       calculation.

  So for route computation, it doesn't matter if you advertise your
 summaries as TVL128 or TVL130. So if it doesn't create routing loops,
 doesn't create suboptimal routing, and doesn't create interoperability
 problems, this problem is non-relevant. Some routers can advertise their
 summaries in TVL128, some might advertise summaries in TVL130. No problem.

  Pick whatever you like best .....
 Hope this helps.

       henk.