From: Dergez Bertalan (dergez@omikron.hu)
Date: Fri Sep 23 2005 - 09:43:17 GMT-3
cciein2006@yahoo.com wrote:
>Thanks Andrew - this does help. Do you have any links to a document describing the ospf path selection process i.e. backbone routers preferred over intra area etc.
>
>_______________________________________________________________________
>Subscription information may be found at:
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>
Intra area routes preferred over inter area routes. All inter area
routes has to go through area 0.
From the rfc2328:
"3.2. Inter-area routing
When routing a packet between two non-backbone areas the
backbone is used. The path that the packet will travel can be
broken up into three contiguous pieces: an intra-area path from
the source to an area border router, a backbone path between the
source and destination areas, and then another intra-area path
to the destination. The algorithm finds the set of such paths
that have the smallest cost.
Looking at this another way, inter-area routing can be pictured
as forcing a star configuration on the Autonomous System, with
the backbone as hub and each of the non-backbone areas as
spokes.
The topology of the backbone dictates the backbone paths used
between areas. The topology of the backbone can be enhanced by
adding virtual links. This gives the system administrator some
control over the routes taken by inter-area traffic."
For the whole document go to: http://www.ietf.org/rfc.html
You can find here more than enough on the topic. First get the Doyle
Routing TCP/IP I book. That's great source and written in more
understandeable fashion. As we could read on the list the new edition
will be out soon.
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