Re: OSPF Area Types

Hey Joseph,

Check out this link. I think it will help you understand why you might have
the no-redistribution option with a NSSA. Essentially, it is a filtering
mechanism that would be used typically in a situation where a NSSA ABR is
also acting as an ASBR at the same time. In that case, what would normally
happen is that the ASBR would inject type-5 LSAs into the backbone and
type-7 LSAs into the NSSA at the same time. The no-redistribution option
filters the type-7 LSAs from being injected into the NSSA

You accomplish a similar goal as having a totally stubby area but they are
distinctly different things. For example, what if you have a situation
where the router acting as the ABR / ASBR is not the ONLY ASBR in the NSSA?
Maybe you don't want to inject certain external routes into your NSSA that
are attached to that ABR/ASBR but still want to allow other external routes
to come into the NSSA from another ASBR. If you had a totally stub area
that would not be possible.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a88.shtml

HTH

On Tue, Jul 5, 2011 at 5:23 PM, Joseph Dougherty <jdougherty_at_jwdougherty.com
> wrote:

> Can someone please tell me if the following table is correct?
>
> http://i.imgur.com/GTARc.png
>
> If so, I'm a bit confused about these different area types / options. What
> is the purpose of the NSSA Totally Stub with the no-redistribute parameter
> applied; isn't this identical to a regular Totally stub network? And what
> about the NSSA Totally Stub with the no-redistribute and default
> information
> originate parameters, isn't that just a regular stub?
>
> Thanks!
>
> Joseph
>
>
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Regards,
Joe Astorino
CCIE #24347
Blog: http://astorinonetworks.com
"He not busy being born is busy dying" - Dylan
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