Howard,
I wish you had edited these Ciscopress books so i wouldn't have to resort to
copy, print and paste (literally) your explanations to their respective
chapters.
Thank you.

Elmer
----- Original Message -----
From: "Howard C. Berkowitz" 
To: 
Sent: Wednesday, January 30, 2002 9:56 PM
Subject: Re: Default-informatin originate always [7:33729]


> >Regarding this command...
> >"Default-information originate [always]"
> >this is documented as saying...
> >this generates the default route into OSPF even if the path to the
default
> >route goes down...
> >and...
> >even when the router has no default route, with the magic keyword
"always"
> it
> >will create a "default route"...pointing to where??
> >Q: What's the point of advertising a route if it is indeed DOWN? Isn't
this
> >like saying i know that Exit5 is closed but I'm gona keep directing all
> >motorists to go to Exit 5 anyway?
> >
> >Please clarify this for me.
> >
> >Elmer
>
> Imagine you have a fairly large OSPF area. If the default route goes
> down, all the topological databases have to be updated and
> propagated.  While if JUST the default route were involved, the
> Dijkstra computation will not have to be run, there still will be
> bandwidth and processor utilization.
>
> If there is only one router generating default, and it goes down, the
> traffic is going to fail anyway. To take your traffic analogy,
> default-information always is indeed like directing the traffic
> LEAVING THE AREA to Exit 5, but not otherwise disturbing those cars
> that don't care about Exit 5.
>
> If there's more than one default router, you definitely don't want
> the always keyword.
>
> Now--as far as where it points: "it depends".  All it points to is
> the router generating default. That router may or may not have a
> default route of its own -- it might be a default-free BGP router as
> well as an ASBR. It could have a default route of its own that points
> somewhere outside the AS or area.
>
> AFAIK, if the router was default-free, you couldn't use
> default-information originate without always, because the router
> would never have a local default to meet the ALWAYS condition.   In
> that case, you'd have to have BGP or a static route specify it, and
> redistribute that route into OSPF.




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