thank you ,my learn-ed friends.....
it seems asif i am finally getting it
>From: "John Neiberger"
>Reply-To: "John Neiberger"
>To: [EMAIL PROTECTED]
>Subject: RE: OSPF Hub and Spoke [7:9268]
>Date: Fri, 22 Jun 2001 10:46:15 -0400
>
>I don't know about the genius part. >:-) But, you've described the
>initial scenario I was asking about. In my original post I wasn't
>suggesting that this would be a good design by any means. I simply was
>wondering if it was possible and how you'd configure it.
>
>In this particular case, the hub router is participating in 20 areas
>which would cause it to be very busy, especially if the network wasn't
>very stable. It would be better to extend area zero across the WAN
>links to insulate the hub router from any instability in the outlying
>areas.
>
>John
>
> >>> "Stephen Skinner" 6/22/01 4:50:10 AM >>>
>Guys,
>
>lets see how my ospf is going ......
>
>in this design goal i would have thought you would have done this ....
>
>
>hub and spoke....at the hub you have say 1 router (3620) with one
>interface
>and 20 sub-interfaces.......
>
>you also have 20 totally stubby area`s which connect into the hub...
>
>config each stub as area 1 through 20
>
>setup each sub int as per area`s 1-20
>
>then setup the lan int as area 0
>
>this way you have one router (hub) which is in area 0 and all the
>other
>area`s aswell........
>
>problem solved ????..
>
>
>something tells me i`ve just either
>
>A got it right and am a genius
>B completely missed the point and broken every rule of ospf
>
>
>YOU DECIDE
>
>steve
>
>
> >From: "Chuck Larrieu"
> >Reply-To: "Chuck Larrieu"
> >To: [EMAIL PROTECTED]
> >Subject: RE: OSPF Hub and Spoke [7:9268]
> >Date: Fri, 22 Jun 2001 01:15:31 -0400
> >
> >John, this one's got me to thinking a little bit. Your kinda right but
>
> >kinda
> >wrong.
> >
> >The areas are an OSPF structure, used for the building of the SPF
>tables.
> >It's not that inter area traffic has to go through a discreet area 0,
>but
> >that in OSPF in order for an area to learn about routes to another
>area
> >there has to be an area 0 router in between them. It does not matter
>if
> >there are a number of interfaces that are ABR's, or if there is a
>discrete
> >and pure area 0.
> >
> >With OSPF, all that matters is that the appropriate adjacencies are
>formed,
> >and that the LSA's are processed and that the OSPF database is
>created. If
> >all that occurs, OSPF routes will be placed into the routing tables.
>As far
> >as the router itself is concerned, routing is independent of the
>routing
> >protocols involved.
> >
> >I've fooled with this in the past. I'll have to do another Q&D lab to
>
> >gather
> >some evidence, and post it here over the weekend.
> >
> >In the meantime, for those interested in some in-depth discussion of
> >routing, Howard's white paper on Certification Zone is definitely
>worth
> >reading. I have not seen the likes of it in any other source,
>including
> >Doyle ( although it has been too long since I've read Doyle )
> >
> >Chuck
> >
> >
> >-----Original Message-----
> >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf
>Of
> >John
> >Neiberger
> >Sent: Thursday, June 21, 2001 6:55 AM
> >To: [EMAIL PROTECTED]
> >Subject: Re: OSPF Hub and Spoke [7:9268]
> >
> >Yes, I'm replying to myself.
> >
> >While doing some reading it occurred to me why *not* extending area 0
>
> >across
> >the WAN links should not work. In OSPF, unlike IS-IS, an area is
>defined
> >by
> >links, not routers. The rule states that interarea traffic must go
>through
> >area 0. Well, if areas are defined by links, then this means that
> >interarea
> >traffic must at least go across one link that is defined as an area 0
>link.
> >
> >In a hub-and-spoke environment with a single hub router, it seems to
>me
> >that
> >there just is no good way to use multiarea OSPF if you don't extend
>area 0
> >across the WAN links.
> >
> >At least, that's the way it appears at the moment.
> >
> >John
> >
> >| I'm having trouble wrapping my brain around a specific scenario and
>I
> >| wanted to get your thoughts. Let's say we have a hub and spoke
>network
> >| with a single router as the hub. There are five areas attached to
>the
> >| backbone. It seems that we would have to extend area 0 across the
>WAN
> >| links, but I'm wondering what would happen if we didn't.
> >|
> >| If we didn't, the backbone router would have no interfaces in area
>0.
> >| I'm wondering if this would cause some major problems. I bet that
>it
> >| would but I'm having a hard time thinking through what actual
>problems
> >| might arise. Would this backbone router just "know" that it was
>area 0
> >| because it has interfaces in multiple non-zero areas and hence
>behave
> >| correctly?
> >|
> >| One obvious problem is that the backbone router would be a member
>of
> >| every area and would thus be pretty busy if the network got to be
>very
> >| big. If we extended area 0 across the WAN link the backbone
>router
> >| would be protected from running SPF calculations everytime a remote
>area
> >| had a link change.
> >|
> >| What other problems would arise? Would this even work at all? I
>don't
> >| really have the tools to try it or I'd just attempt this chaos
>myself.
> >| As you can guess, we run eigrp everywhere so I'm still clueless to
>some
> >| of the workings of OSPF in a production environment.
> >|
> >| Regards,
> >| John
> >|
> >|
> >|
> >|
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