Let me state first of al that I do not know the genesis of this question. It
originated on another news group, and there were a number of responses that
stated "use virtual links"
I thought about the implication of the question, and asked myself "in OSPF,
do areas have to have unique numbers?" The answer is interesting. Looked up
RFC 2328, the current OSPF standard, and found the following rather
interesting paragraph:
-----------------------
3.7. Partitions of areas
OSPF does not actively attempt to repair area partitions. When an area
becomes partitioned, each component simply becomes a separate area. The
backbone then performs routing between the new areas. Some destinations
reachable via intra-area routing before the partition will now require
inter-area routing. However, in order to maintain full routing after the
partition, an address range must not be split across multiple components of
the area partition. Also, the backbone itself must not partition. If it
does, parts of the Autonomous System will become unreachable.
Backbone partitions can be repaired by configuring virtual links (see
Section 15).
-----------------------
In other words, the configuration as described below is a legal OSPF
construction. One may have multiple areas of the same number. The only
caveat appears to be that the address space cannot overlap.
I still have not heard from the person who posted the original question as
to why it was asked. Was it a matter of an area that had two links into the
backbone that through bad things happening, became partitioned? Or was it a
matter of somebody just did it that way.
Someone else asked in anther thread if anyone thought Caslow was the
greatest. I personally find Caslow's approach to be outstanding, and worth
studying. I can say the same about a few other writers I have read, some of
whom participate here on groupstudy. Problems such as this one provide a
clue as to why.
Chuck
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
Chuck Larrieu
Sent: Monday, August 14, 2000 9:52 PM
To: Cisco Mail List
Subject: OSPF question - discontiguous areas
This question came up on another list. I thought I would repeat it here, and
see what kind of discussion it engenders.
Question: how does one repair a discontiguous OSPF area?
e.g. Area_2---------Area_0-----------Area_2
How would you go about it?
Chuck
----------------------
I am Locutus, a CCIE Lab Proctor. Xx_Brain_dumps_xX are futile. Your life as
it has been is over ( if you hope to pass ) From this time forward, you will
study US!
( apologies to the folks at Star Trek TNG )
http://www.cl.cncdsl.com/Locutus.html
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