Can someone perhaps help educate me here. I have now seen this on a couple
of posts, did a bit of reading, and have learned that stub and totally
stubby areas are not necessarily limited to a single ingress/egress point.
I.e. can have more than one ABR.
Area0-------Area1 area 1 is a stub area ( or totally stubby, depending
upon the LSA, summarization, and default route handling )
Area0------Area1_ABR1
|------Area1_ABR2 still a stub area / totally stubby area
What makes and area NOT a stub area? Is it only the summarization / LSA /
default route handling?
Yes I understand the NSSA, with its ABSR connecting to an outside AS and
that information being passed into an OSPF domain in a particular manner.
I guess the question is this: other than the NSSA, is EVERY OSPF area either
stub or totally stubby?
Area0---------Area1-------|
| ABR?
|---------Area2--------|
would the above layout make and area NOT stubby or totally stubby?
Chuck
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
Peter A van Oene
Sent: Saturday, November 11, 2000 8:01 PM
To: [EMAIL PROTECTED]
Subject: Re: OSPF Totally Stubby Areas and area default-cost
Totally stubby is a cisco nob that takes the concept of a stub area a step
further. In a stub area, only LSA types 1 (router) 2 (network) and 3
summary) flow within the area. Hence, no routing information concerning
prefixes outside of the OSPF domain is injected into the area. In a totally
stubby area, the flow of normal type 3 LSA's is halted as well. This leaves
the area with no information about any prefixes outside of the area. In
order to allow traffic to exit the area, a single type 3 LSA is propagated
by each ABR which advertises a default route. The default cost nob simply
allows you to set a cost for the route instead of using the standard OSPF
metric to the ABR itself.
Hope this helps some
Pete
*********** REPLY SEPARATOR ***********
On 11/08/2000 at 4:29 PM Bob Hunter wrote:
>Hi,
> I'm confused on the subject of totally stubby areas, and the command "area
>default-cost". From what I'm reading, one of the qualifications of a
totally
>stubby area is that if multiple exits (ABRs) exist, routing to outside the
>area does not have to take an optimal path. Does this mean that each router
>within the area picks the closest ABR as the gateway to everything outside
>the area, and that there is no way to control the default route? If so,
does
>that imply that the area default-cost is used for incoming routes? Would
>incoming routes even exits if the area was a totally stubby area?
>
> I would very much appreciate it if someone would please set me straight.
>
> Thank you.
>
>Bob Hunter, CCNA, CNE
>
>
>
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