Re: Why a transit area cannot be a stub area?

Stubs were also created with the option of not allowing type 3 LSAs (this is
from page 133 of Moy's book "OSPF: Anatomy of an Internet Routing Protocol).
I think this would blackhole traffic heading from the backbone toward the
disconnected area because the stub would not have the type 3 LSAs for the
disconnected area, just like it would type 5 LSAs. Section 12.4.3.1 of RFC
2328 may give a little more insight regarding this "option" for summary
LSAs.

On Mon, Aug 24, 2009 at 5:34 PM, Hoogen <hoogen82_at_gmail.com> wrote:

> Hi Darby,
> I was referring a transit area which connects disconnected area's. Sorry
> for
> the confusion.
>
> The question was Why can't we have the area's that have virtual-links to be
> a stub area. RFC says you can't " the only reason being if the disconnected
> area had ASBR's we have a problem transmitting Type 5 LSA's
>
>
> http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094aaa.shtml#virtuallinks
>
> Please have a look @ line 3 of the first paragraph.." The transit area
> cannot be a stub area". I understand it why.. like Scott pointed out.. but
> I
> was hoping if we do not have asbr's in the disconnected area.. there should
> be a better answer. Best practice you do not configure it.. but just was
> digging around for a better explanation.
>
> -Hoogen
>
>
>
> On Mon, Aug 24, 2009 at 4:13 PM, Darby Weaver <darby.weaver_at_gmail.com
> >wrote:
>
> > Hmm...
> >
> > I define area a transit Area as "The Transit area" aka Area 0.
> >
> > Now since Area 0 is connected to every other area it seems contracdictory
> > to me and my viewpoint to ever declare it a stub area.
> >
> > Each area attached to Area 0 sends its information to Area 0.
> >
> > Virtual-links are an extension of Area 0.
> >
> > So with all that said... what was the question again?
> >
> > I have a pretty nice powerpoint that kinda illustrates the whole picture
> > and I guess if you stare at it long enough it starts to make sense. :)
> >
> >
> >
> >
> >
> >
> >
> >
> > On Mon, Aug 24, 2009 at 5:15 PM, Hoogen <hoogen82_at_gmail.com> wrote:
> >
> >> Hi All,
> >> I have been trying to look around but any more information would be
> >> great...
> >>
> >> The only thing I understand it can't be done is because RFC says so..
> and
> >> because just in case the disconnected area has ASBR type 5 external
> lsa's
> >> cannot pass through.
> >>
> >> Anyone has any more information other than this?
> >>
> >> -Hoogen
> >>
> >>
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Bryan Bartik
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Sr. Support Engineer - IPexpert, Inc.
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