That's another question I had. I'm going to go lab test this today and will
report my findings.
Thanks everyone,
Ralph
""Wilson, Bradley"" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> The question that's on my mind is where you have an area which has
multiple
> ABRs. Do the internal routers simply compare the metrics to the
respective
> ABRs and make their routing decision based on that comparison?
>
> BJ
>
>
>
> -----Original Message-----
> From: Howard C. Berkowitz [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, August 15, 2001 9:44 AM
> To: [EMAIL PROTECTED]
> Subject: Re: OSPF Distance Vector in the backbone? [7:16120]
>
>
> While I agree completely with Peter's statements, I think there may be two
> issues being mingled.
>
> Area 0.0.0.0, especially when there are no backbone-only routers, uses a
> DV-like algorithm to
> propagate inter-area and exterior routes. There's no use for a Dijkstra.
>
> Inside a nonzero area, the Dijkstra algorithm only computes intra-area
> routes, with a computational
> workload on the order of the square of the number of routes plus the
> logarithm of the number of routers.
> Inter-area and external routes are added to the routing table of that area
> as a second step, the workload for
> which is linear with the number of non-intra-area routes.
>
> At 08:55 AM 8/15/2001 -0400, you wrote:
> >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:
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