Subject: Re: overlapping area ranges

From: "Jeyanath Minto J - CTD, Chennai." <[email-masked]>
Date: Mon, 21 Oct 2002 19:42:36 +0530

hi Kostiner,

  otherwise we end up with routing Loop.
  assume that two routers are advertise same 10/8 route.
  both the routers think others having route to unreachable destination(
like 10.2.4/24 ) and forward to each other .

  discard route solve this problem by
           " if we dont have the exact match and the route entry is discard
entry then drop it "

Minto

-----Original Message-----
From: Kostiner, Assaf (Assaf) [mailto:[email-masked]]
Sent: Monday, October 21, 2002 7:10 PM
To: [email-masked]
Subject: overlapping area ranges

Hi,
I'm trying to understand the exact problem with aggregating all subnets of
10.0.0.0/8 in one area, and having an address 10.2.3.4 in another area.
When trying to find the best-match, we always go to the more specific IP
address anyway, so 10.2.3.4 should always be reachable. no?
Why then, in RFC 1583, they prevented this configuration, by preventing the
border router which aggregates the 10.0.0.0 range, from accepting summaries
which fall into this range?
Why in the later RFCs, they added the following paragraph (under 11.1):
"Before the lookup begins, "discard" routing table entries should be
inserted into the routing table for each of the router's active area address
ranges (see Section 3.5). (An area range is considered "active" if the range
contains one or more networks reachable by intra-area paths.) The
destination of a "discard" entry is the set of addresses described by its
associated active area address range, and the path type of each "discard"
entry is set to "inter-area".[10] "
What is its contribution?
I would appreciate any help with the above. Thanks in advance, Assaf.