Re: Inter-area routes reachable via multiple areas

Vivek Dubey <vivek_ospf@REDIFFMAIL.COM> Wed, 10 September 2003 10:15 UTC

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Date: Wed, 10 Sep 2003 10:13:25 -0000
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From: Vivek Dubey <vivek_ospf@REDIFFMAIL.COM>
Subject: Re: Inter-area routes reachable via multiple areas
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The case should not occur in case of standard ABR implementations for inter-area route calculations.
CISCO/IBM ABR implementations might lead to such scenario.

Vivek




On Wed, 10 Sep 2003 Liu Yu wrote :
>Hi! all
>
>I notice that the clause in  RFC 2328 16.4 (3) is just for external route.
>How about "inter-area routes"ï¼ RFC 2328 does not explicitly state this
>one! Just choose the "the path whose associated area has the
>largest OSPF Area ID "ï¼ï¼ Maybe every one has his own implentation.
>
>
>thanks!
>
>
>----- Original Message -----
> From: "Acee Lindem" <acee@REDBACK.COM>
>To: <OSPF@PEACH.EASE.LSOFT.COM>
>Sent: Friday, August 01, 2003 5:46 AM
>Subject: Re: ASBR reachable via multiple areas
>
>
> > Rob,
> >
> > You are correct - I missed that clause in 16.4 (3) when
> > re-reading. I should have checked my implementation before
> > replying. I can't envision why installing an equal-costs
> > routes through multiple areas using the same 16.4.1 selection
> > rules could cause a routing loop or other problem.
> >
> > Thanks,
> > Acee
> >
> > ROB PATH wrote:
> > > --- Acee Lindem <acee@REDBACK.COM> wrote:
> > >
> > >>Igor Miroshnik wrote:
> > >>
> > >>>All,
> > >>>
> > >>>   RFC 1583 states: "AS boundary router's routing
> > >>
> > >>table entry must indicate a set of paths which
> > >>
> > >>>utilize a single area." (16.1)
> > >>>   Why not utilize all equal-cost paths through
> > >>
> > >>different areas?
> > >>
> > >>Hi Igor,
> > >>
> > >>I believe you can calculate equal cost paths through
> > >>multiple
> > >>areas - read section 16.4 and 16.4.1 in RFC 2328
> > >>(which
> > >>obsoletes RFC 2178 which obsoletes RFC 1583).
> > >>
> > >>
> > >
> > >
> > > The section 16.4 in RFC 2328 does not explicitly state
> > > that equal cost paths through multiple areas could be
> > > utilized (say for load balancing purposes).
> > >
> > > It rather states that when there are multiple
> > > least cost paths available in the routing
> > > table, the path whose associated area has the
> > > largest OSPF Area ID is chosen.
> > >
> > > Also section 16.4.1 refers to section 16.4 for
> > > choosing a path based on cost, when there are
> > > multiple paths of equal highest preferences.
> > >
> > > So it essentially means that multiple equal cost
> > > inter-area paths are not utilized.
> > >
> > > Thanks,
> > >     Rob.
> > >
> > >
> > >
> > >>
> > >>>   Thanks,
> > >>>   Igor
> > >>>
> > >>
> > >>
> > >>--
> > >>Acee
> > >
> > >
> > >
> > > =====
> > > Rob Path
> > > E-Mail : rob_path@yahoo.com
> > >
> > > __________________________________
> > > Do you Yahoo!?
> > > Yahoo! SiteBuilder - Free, easy-to-use web site design software
> > > http://sitebuilder.yahoo.com
> > >
> >
> >
> > --
> > Acee
>

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Re: Inter-area routes reachable via multiple areas Vivek Dubey
Re: Inter-area routes reachable via multiple areas Liuyu
Re: Inter-area routes reachable via multiple areas Acee Lindem
Re: Inter-area routes reachable via multiple areas Liu Yu
Re: Inter-area routes reachable via multiple areas Acee Lindem