From: mam phuquoc (mamphuquoc@gmail.com)
Date: Wed Aug 08 2007 - 14:39:55 ART
Wow, this is really great info. This is actually production and currently
we only have one ABR router bordering nssa5 and area 0. I'm planning a
second ABR that borders both area 0 and area nssa5 and have another area 0
link to the first ABR, and they need to redistribute some
routes to other routers in area 0, and I don't have spare equipement to test
this in advance.
So ultimately, building 3 router will hear route 10.0.0.0 from area 0 at
building 1, and the nssa route 10.0.0.0 from building 2, and regardless of
what area the route is sourced from, it uses ABR 2 to get there, it will
send the traffic to the ABR2, and ABR 2 will always send that traffic to
nssa area 5 because it preferes nssa routes over E1 route from building 1.
Can anyone confirm this? Thanks.
Building 1 redistributing route 10.0.0.0 into area 0 ------->
area0 ------------------------------------------ABR
1------------------------------nssa 5
| |
|
|
area
0 Building2 nssa 5
| |
Building
3 |
|
area0 ---------------------------------------- ABR
2----------------------------------nssa 5
<--------------Building 2 redistributing route 10.0.0.0 into
nssa 5
On 8/8/07, Darren Johnson <dazza_johnson@yahoo.co.uk> wrote:
>
> 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
> > > >
> > > >
> >
> _______________________________________________________________________
> > > > Subscription information may be found at:
> > > > http://www.groupstudy.com/list/CCIELab.html
> > > >
> > >
> > >
> > >
> > > --
> > > Kindest regards,
> > > hm
> >
> >
> _______________________________________________________________________
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> >
>
>
>
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