RE: OSPF non-backbone area

From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Tue May 03 2005 - 13:50:53 GMT-3


Short answer, no. Long answer:

RFC 2328 - OSPF Version 2

    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).

Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)

bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Tuesday, May 03, 2005 9:37 AM
To: Group Study
Subject: OSPF non-backbone area

Hi guys,
 
Why is the following topology OK?
 
r1 area 1 r2 area 0 r3 area 1 r5
                           |
                          r4
                           |
                      area 1
 
Notice that there are multiple non-contiguous area 1's.
 
Are there any limitations regarding using non-unique non-backbone areas
multiple times?
 
Or, can the same area number be used for any non-backbone area
regardless of
any other topology considerations?
 
TIA, Tim



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