From: Narbik Kocharians (narbikk@gmail.com)
Date: Fri Jan 04 2008 - 14:46:39 ARST
No worries Luan anytime.
On 1/4/08, Luan Nguyen <luan.m.nguyen@gmail.com> wrote:
>
> Thanks everyone for helping. Especially Narbik for the material!
> I learned quite a bit.
> I learned that i need to read better. Learned about area range
> not-advertise, area filter-list, use more specific show command like show
> ip
> ospf database x.x.x.x to get more detail...etc.
>
> -lmn
>
> On Jan 4, 2008 6:33 AM, Paul Cosgrove <paul.cosgrove@heanet.ie> wrote:
>
> > A NSSA ASBR creates a type-7 external LSA and sets the forwarding
> > address. Unlike with other areas ASBRs which only sometimes set this
> > value, an NSSA ASBRs will always set it.
> >
> > The NSSA ABR then translates this type-7 LSA into a type-5. While it
> > will specify itself as the advertising router in the type-5, it includes
> > the same forwarding address that it received in the ASBRs type-7 LSA.
> >
> > Routers in different area which receiving the type-5, will check to see
> > that the forwarding address is accessible via an inter area route. They
> > will only use the LSA if such a route is found, otherwise it is ignored.
> >
> > If you have a requirement to suppress type-1 and type-2 LSAs from your
> > NSSA area into other areas, then you may use area range with the
> > not-advertise option to filter the unwanted routes. This is the example
> > given on the cisco link you mentioned but filtering using an area
> > filter-list or distribute-list etc. can also cause the same issue.
> >
> > The problem occurs when the route to the forwarding address IP of the
> > translated type-5 is filtered out, so it no longer advertised into other
> > areas.
> >
> > When a receiving router checks the type-5 forwarding address and find it
> > has no route to that IP, it sees the advertised route as inaccessible
> > and ignores the type-5 LSA.
> >
> > If you set the ABR to override the ASBRs forwarding address and instead
> > specify itself in the forwarding address field (actually using 0.0.0.0
> > in its advertisement, which is understood to mean itself), then the
> > other routers will still accept the type-5.
> >
> > Paul.
> >
> > Luan Nguyen wrote:
> > > Can I look at the workbook also? :)
> > > Would someone kind enough to explain this? I found this:
> > >
> >
> http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a00804556e5.html
> > > but I don't see any different with that area XX nssa translate type7
> > > suppress-fa command. By default, the NSSA ABR already used itself to
> > > advertise those type5-translated-from-type7 LSA to its neighbors.
> What
> > is
> > > the deal here?
> > >
> > > -lmn
> > >
> > > On Jan 3, 2008 8:21 PM, Narbik Kocharians <narbikk@gmail.com> wrote:
> > >
> > >> Look at the last lab in your OSPF section. From the work book in the
> > class
> > >> room.
> > >>
> > >> On 1/3/08, Chris Riling <criling@gmail.com> wrote:
> > >>> Hi Group,
> > >>>
> > >>> Does anyone have a good explanation for "area nssa translate"?
> > Frome
> > >>> the DocCD:
> > >>>
> > >>> area nssa translate
> > >>>
> > >>> To configure an area as a not-so-stubby area (NSSA) and configure
> the
> > >> Open
> > >>> Shortest Path First (OSPF) Forwarding Address Suppression in
> > Translated
> > >>> Type-5 LSAs feature, use the *area nssa translate *command in router
> > >>> configuration mode. To remove the NSSA distinction from the area,
> use
> > >> the
> > >>> *
> > >>> no* form of this command.
> > >>>
> > >>> *area* *area-id* *nssa* *translate type7 suppress-fa *
> > >>>
> > >>> no *area* *area-id* *nssa* *translate type7 suppress-fa *
> > >>> Syntax Description
> > >>>
> > >>> *area-id*
> > >>>
> > >>> Identifier of the area for which authentication is to be enabled.
> The
> > >>> identifier can be specified as either a decimal value or an IP
> > address.
> > >>>
> > >>> *translate*
> > >>>
> > >>> Translates one type of LSA to another type of LSA. This keyword
> takes
> > >>> effect
> > >>> only on an NSSA area border router (ABR) or NSSA Autonomous System
> > >>> Boundary
> > >>> Router (ASBR).
> > >>>
> > >>> *type7*
> > >>>
> > >>> Translates a Type-7 LSA to a Type-5 LSA. This keyword takes effect
> > only
> > >> on
> > >>> an NSSA ABR or an NSSA ASBR.
> > >>>
> > >>> *suppress-fa*
> > >>>
> > >>> Suppresses the forwarding address of the Type-7 LSAs from being
> placed
> > >> in
> > >>> the Type-5 LSAs. This keyword takes effect only on an NSSA ABR or an
> > >> NSSA
> > >>> ASBR.
> > >>>
> > >>> Doesn't an NSSA ABR do this by it's very nature? Also, could someone
> > >>> clarify
> > >>> when you might use forward address supression?
> > >>>
> > >>> Thanks,
> > >>> Chris
> > >>>
> > >>>
> > _______________________________________________________________________
> > >>> Subscription information may be found at:
> > >>> http://www.groupstudy.com/list/CCIELab.html
> > >>>
> > >>
> > >>
> > >> --
> > >> Narbik Kocharians
> > >> CCIE# 12410 (R&S, SP, Security)
> > >> CCSI# 30832
> > >> www.MicronicsTraining.com
> > >> Sr. Technical Instructor
> > >> www.Net-WorkBooks.com
> > >>
> > >>
> _______________________________________________________________________
> > >> Subscription information may be found at:
> > >> http://www.groupstudy.com/list/CCIELab.html
> > >
> > >
> _______________________________________________________________________
> > > Subscription information may be found at:
> > > http://www.groupstudy.com/list/CCIELab.html
> > >
> >
> >
> > --
> > Paul Cosgrove
> > HEAnet Limited, Ireland's Education and Research Network
> > 1st Floor, 5 George's Dock, IFSC, Dublin 1
> > Registered in Ireland, no 275301
> > tel: +353-1-660 9040 fax: +353-1-660 3666
> > web: http://www.heanet.ie/
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
-- Narbik Kocharians CCIE# 12410 (R&S, SP, Security) CCSI# 30832 www.MicronicsTraining.com Sr. Technical Instructor www.Net-WorkBooks.com
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