From: NN Kumar (nagendra.cisco@gmail.com)
Date: Fri Aug 15 2008 - 13:47:58 ART
Hi,
When there are 2 ABRs connected to NSSA area as in your topology, the ABR
with highest router-id will be the one to do type-7 to type-5 LSA
translation. So in your case, rC would be the ABR with highest router-id.
Regards,
Nagendra
On Fri, Aug 15, 2008 at 3:26 PM, <daniel.yusuf@nsn.com> wrote:
> hello all, actually it is a general question... however, thanks for any
> response...
>
> the topology is simply as follow
>
> |------- rD --------|
> rA ------| |-------rB
> |--------rC---------|
>
>
> rA - rD - rC in NSSA
> rB - rD - rC in backbone.
> rA is redistributing static route into OSPF,
>
> while typing sh ip ospf command in both ABR, only rC Perform type-7/type-5
> LSA
> translation. see the following truncated response.
>
> then i was thinking wether rD is/ is not doing type-7/type-5 translation ??
>
>
>
> rD#sh ip osp
>
> Area 1
> Number of interfaces in this area is 2
> It is a NSSA area
> Area has no authentication
> SPF algorithm last executed 00:14:26.248 ago
> SPF algorithm executed 7 times
> Area ranges are
> Number of LSA 10. Checksum Sum 0x02BF96
> Number of opaque link LSA 0. Checksum Sum 0x000000
> Number of DCbitless LSA 0
> Number of indication LSA 0
> Number of DoNotAge LSA 0
> Flood list length 0
>
>
>
> rC#sh ip osp
> Area 1
> Number of interfaces in this area is 2
> It is a NSSA area
> Perform type-7/type-5 LSA translation
> Area has no authentication
> SPF algorithm last executed 00:13:51.888 ago
> SPF algorithm executed 10 times
> Area ranges are
> Number of LSA 10. Checksum Sum 0x02BF96
> Number of opaque link LSA 0. Checksum Sum 0x000000
> Number of DCbitless LSA 0
> Number of indication LSA 0
> Number of DoNotAge LSA 0
> Flood list length 0
>
>
>
>
>
>
>
> ________________________________
>
> From: ext Hobbs [mailto:deadheadblues@gmail.com]
> Sent: jeudi 14 ao{t 2008 22:01
> To: Daniel Valle
> Cc: Yusuf Daniel (NSN - MA/Rabat); ccielab@groupstudy.com
> Subject: Re: P-bit in NSSA ABR
>
>
> Daniel (the first one Mr. Yusef), can you post your task and topology? I am
> curious to know what is the requirement :)
>
> thanks
>
>
> On Thu, Aug 14, 2008 at 2:24 PM, Daniel Valle <danielfrvalle@gmail.com>
> wrote:
>
>
> I think the correct question maybe is (Daniel, please correct me I'm
> wrong!)... How not to convert LSA type-7 to type-5 because by
> default it is
> converted. The P bit is set to one.
>
> I had the same doubt a couple of years ago.
>
> Let me see if this helps. From Jeff Doyle's book:
>
> "The NSSA External LSA has a flag in its header known as the P-bit.
> The NSSA
> ASBR has the option of setting or clearing the P-bit. If the NSSA's
> ABR
> receives a type 7 LSA with the P-bit set to one, it will translate
> the type
> 7 LSA into a type 5 LSA and flood it throughout the other areas. If
> the
> P-bit is set to zero, no translation will take place and the
> destination in
> the type 7 LSA will not be advertised outside of the NSSA. This
> option
> allows you to design an NSSA in which the external destinations
> learned in
> that area are known only in that area."
>
> I got a bit confused with the explanation above because the IOS has
> the
> command: "area x nssa no-redistribute".
>
> This command only works when the router is altogether an ASBR, ABR,
> and is
> connected to a NSSA area AND area zero
>
> the diagram below illustrates an example where the "area x nssa
> no-redistribute" does not make any filtering to avoid the RIP route
> comming
> to area 0.
>
> (RIP)<--R1-->(OSPF NSSA AREA)<--R2-->(OSPF AREA 0)<--R3
>
>
> You cannot filter at R2 the LSA Type-7 which was generated by R1.
> the only
> way to do it would be ( from the book troubleshooting ip routing
> protocols):
>
> "summary-address x.x.x.x x.x.x.x not-advertise
>
> This summary-address configuration generates a Type 7 LSA that won't
> be
> translated into a Type 5 LSA by the NSSA ABR.
> "
>
>
> It would only work in this topology: R2 redistributing the RIP
> routes to
> area 0 and not to nssa area
>
>
> *(RIP)*
> |
> R1-->(OSPF NSSA AREA)<--R2-->(OSPF AREA 0)<--R3
>
>
> Configure the no-redistribution command on an NSSA ABR that's also
> an ASBR.
> ( R2 in the example)
>
>
>
> Hope this helps,
>
> Daniel Valle
>
> On 8/13/08, Scott Morris <smorris@internetworkexpert.com> wrote:
> >
> > Are you asking in general, or for a particular lab assignment?
> >
> > "Manually", I'd say that you'll be sitting by a router looking to
> change
> > things in packets, but that's time consuming and detailed work
> that nobody
> > wants. :)
> >
> > First ask what is the P-bit? Then you may find the answer leaps
> out a
> > little when looking at a few commands.
> >
> > But a little more context to your question may help me give a
> better
> answer
> > to you! (Check out RFC 3101)
> >
> > HTH,
> >
> >
> > Scott Morris, CCIE4 #4713, JNCIE-M #153, JNCIS-ER, CISSP, et al.
> > CCSI/JNCI-M/JNCI-ER
> > Senior CCIE Instructor
> >
> > smorris@internetworkexpert.com
> >
> >
> >
> > Internetwork Expert, Inc.
>
> > http://www.InternetworkExpert.com <
> http://www.internetworkexpert.com/>
>
> > Toll Free: 877-224-8987
> > Outside US: 775-826-4344
> >
> > Knowledge is power.
> > Power corrupts.
> > Study hard and be Eeeeviiiil......
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf Of
> > daniel.yusuf@nsn.com
> > Sent: Wednesday, August 13, 2008 11:42 AM
> > To: ccielab@groupstudy.com
> > Subject: P-bit in NSSA ABR
> >
> > Hi GS,
> >
> > How to change P-bit in LSA type-7 at NSSA ABR manually... ?
> >
> > Thanks for your response,
> >
> > -daniel
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
> >
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>
> _______________________________________________________________________
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