From: Scott Morris (smorris@ipexpert.com)
Date: Wed Aug 08 2007 - 12:52:55 ART
That would be my guess, though I deduced it a little differently. :) My
brain latched onto the idea of finding the next hop as a Type 1 (intra-area)
for N1/2 routes versus a Type 4 (inter-area) for E1/2 routes. But the
RFC's always a good thing to look at!
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
VP - Technical Training - IPexpert, Inc.
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-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Darren Johnson
Sent: Wednesday, August 08, 2007 11:22 AM
To: mam phuquoc; Herbert Maosa
Cc: Cisco certification
Subject: Re: NSSA area
What a good question, best I've seen for a while :-)
Check out the NSSA RFC 3101. Here it states:
".......then apply the following priorities in deciding which LSA is
preferred:
1. A Type-7 LSA with the P-bit set.
2. A Type-5 LSA.
3. The LSA with the higher router ID."
The P-bit basically means do you want to translate the Type 7 LSA to a Type
5 LSA at the NSSA ABR. By default, this is set.
IMO, this means NSSA is chosen over Type 5 LSAs as per the above extract
from the RFC.
Anyone else have any comments?
Dazzler
--- mam phuquoc <mamphuquoc@gmail.com> wrote:
> From the router the is the ABR between area 0 and nssa area 5, I see
> that the routing table shows that the same route advertised from area
> 0 as type
> E1 and from nssa area 5 as type nssa 1 , the nssa1
> route from nssa area 5
> is prefered and put in the routing table. I thought route type E1 is
> preferred over nssa1. There is a ospf order IntraArea, Interarea, E1
> and E2, however I can't find anything regarding OSPF preference for
> NSSA1 or 2 compare to Intra area, Interarea, E1 and E2 routes.
>
>
>
>
> On 8/8/07, Herbert Maosa <asawilunda@googlemail.com>
> wrote:
> >
> > Without confirming this in a lab, my opinion is
> that if you have two such
> > routes, you are going to take the path that is
> metrically closer to the ASBR
> > that generated the external route. However if that
> ASBR is in another area,
> > then you will follow Area 0 since all Inter-area
> traffic has to go through
> > area 0, regardless of cost.
> >
> > my two cents worth.
> >
> > Herbert.
> >
> > On 8/8/07, mam phuquoc <mamphuquoc@gmail.com>
> wrote:
> >
> > > Hi all,
> > >
> > > question, if there is an ABR router with some
> interfaces in area 0 and
> > > other
> > > interfaces in nssa area 5. If there is an
> external route redistributed
> > > in
> > > to area 0 as a type E1, and the same route is
> redsitributed into nssa
> > > area
> > > 5, the router acting as the abr will see both in
> the ospf database, but
> > > which one will it use and put in the routing
> table, the nssa route, or
> > > the
> > > E1 route from area 0?
> > >
> > > Is this network topology below valid? Can both
> ABR inject a default
> > > route
> > > into the NSSA area 5 and use metric to pick the
> preferred path? Or can
> > > you
> > > have only one ABR in a NSSA?
> > >
> > > THank you.
> > >
> > >
> > > area0
> > >
>
------------------------------------------ABR-------------------------------
nssa
> > > 5
> > >
> > > | |
> > >
> |
> > > |
> > >
> area
> > > 0 nssa 5
> > >
> > > | |
> > >
> > > | |
> > > area0
> ----------------------------------------
> > > ABR----------------------------------nssa 5
> > >
> > > announcing route 10.0.0.0------->
> <---------------announcing
> > > route 10.0.0.0
> > >
> > >
>
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