From: Narbik Kocharians (narbikk@gmail.com)
Date: Mon Oct 29 2007 - 16:38:07 ART
Look at the "capability transit" command
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hirp_r/rte_osph.htm#wp999437
On 10/29/07, Scott Vermillion <scott_ccie_list@it-ag.com> wrote:
>
> It must flow to Area 0. You cannot build a virtual link directly between
> Areas 1 and 2; all virtual links either connect two pieces of Area0 or
> they
> connect a non-0 area to Area 0. In other words, all virtual links involve
> Area 0!
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> CCIEin2006
> Sent: Monday, October 29, 2007 12:42 PM
> To: Cisco certification
> Subject: Re: Why must all areas connect to Area 0?
>
> So in this scenario
>
> Area1-Area2
> \ /
> Area0
>
> Area 1 and 2 are directly connected. Would the data need to flow to area0
> or
> can the traffic flow directly?
>
> What if we configured a virtual link between them?
>
> On 10/29/07, CCIEin2006 <ciscocciein2006@gmail.com> wrote:
> >
> > Hi folks,
> >
> > I was reading over Jeff Doyle's blog and came across his favorite
> > interview question:
> > Why does OSPF require all traffic between non-backbone areas to pass
> > through a backbone area (area 0)?
> >
> > Answer:
> > Because inter-area OSPF is distance vector, it is vulnerable to routing
> > loops. It avoids loops by mandating a loop-free inter-area topology, in
> > which traffic from one area can only reach another area through area 0.
> >
> > Can someone elaborate on that answer a little bit? Exactly how does
> having
> > a connection to Area0 prevent routing loops? Is it similar to spanning
> tree
> > in the area 0 is the root of the spanning tree?
> >
> > Also this answer does not take into consideration redistribution from
> > another routing protocol right?
> >
> > Thank You
> >
> > Here is the article:
> > http://www.networkworld.com/community/node/19293
>
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-- Narbik Kocharians CCIE# 12410 (R&S, SP, Security) CCSI# 30832 www.Net-WorkBooks.com
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