Hey Ralph,
This statement is quite true. Is there an area you wish to break down more
fully?
For support, see the draft-ietf-ospf-abr-alt-04.txt which includes the
following text:
In OSPF domains the area topology is restricted so that there must be
a backbone area (area 0) and all other areas must have either
physical or virtual connections to the backbone. The reason for this
star-like topology is that OSPF inter-area routing uses the
distance-vector approach and a strict area hierarchy permits
avoidance of the "counting to infinity" problem. OSPF prevents
inter-area routing loops by implementing a split-horizon mechanism,
allowing ABRs to inject into the backbone only Summary-LSAs derived
from the intra-area routes, and limiting ABRs' SPF calculation to
consider only Summary-LSAs in the backbone area's link-state
database.
*********** REPLY SEPARATOR ***********
On 8/15/2001 at 12:12 AM Ralph Fudamak wrote:
>Question about OSPF and LSA type 3 behavior. Doyle in Routing TCP/IP vol
>1:
>
> "When another router receives a Network Summary LSA from an ABR, it
>does
>not run the SPF algorithm. Rather it simply adds the cost of the route to
>the ABR and the cost included in the LSA. A route to the advertised
>destination, via the ABR, is entered into the route table along with the
>calculated cost. This behavior - depending on an intermediate router
>instead of determining the full route to the destination - is distance
>vector behavior. So, while OSPF is a link state protocol within an area,
>it
>uses a distance vector algorithm to find inter-area routes." (pg 474,475)
>
>Please enlighten me.
>
>TIA,
>Ralph
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=16167&t=16120
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