Re: OSPF LSA type 3 filtering

Superb discussion!!!

By the way, remember that in IOS a router does not need to have an
interface in area 0 to be considered an ABR. You may configure the OSPF
process in a VRF and it will become an ABR regardless if it has interfaces
in area 0. You can disable that with capability vrf-lite.

In Marko's example configuring both FastEthernet subinterfaces of R2 in a
VRF and the OSPF as well, will do the trick.

2013/1/3 Narbik Kocharians <narbikk_at_gmail.com>

> Sarad, Tim or whoever that is interested,
>
> Please download a lab that I wrote on OSPF Filtering, I think you will find
> it very useful, it covers many aspects of filtering in OSPF. Let me know
> your thoughts.
>
> Download the following files:
>
> http://micronics.nl/OSPF-Filtering.pdf
> http://micronics.nl/OSPF-Initial-config.txt
>
> Marko,
>
> Very nice blog, and I agree that there can't be a direct summarization
> between non-backbone areas.
>
> On Thu, Jan 3, 2013 at 3:56 AM, Sarad <tosara_at_gmail.com> wrote:
>
> > Hi Brian,
> >
> > If I understood correctly, as per your explanation area-range and
> > filter-list commands come in to effect after ABR construct the type 3 LSA
> > to be generated in to the other Area.
> >
> > When I lab this up I noticed filtering with these commands work
> differently
> > when filter type 3 LSA from one Area to another area. Is there a
> technical
> > explanation for why this happening?
> >
> > Thanks
> > Sara
> >
> >
> >
> > On Thu, Jan 3, 2013 at 8:46 PM, Brian McGahan <bmcgahan_at_ine.com> wrote:
> >
> > > If you want to continue this as a technical discussion that's fine,
> just
> > > don't freak out again after reading my response ;)
> > >
> > > You said:
> > >
> > > > What if in area 1 there are some LSA type-1 and type-2? Can you not
> > > filter them or summarize them with the "area range" command?
> > >
> > > No, you can not. This is a fundamentally incorrect notion about OSPF.
> > > First, both LSA 1 and 2 are area local scope. The ABR cannot pass them
> > > between areas hence there is no filtering or summarization that can
> > affect
> > > them. Secondly, the *topology* information described by these LSAs is
> > > automatically summarized by the ABR into LSA 3. The *reachability*
> > > information is not.
> > >
> > > The reachability information described in multiple LSA 3s can
> summarized
> > > together with the "area range" command. Additionally the reachability
> > > information described in LSA 3 can be filtered with either "area range"
> > or
> > > "area filter-list".
> > >
> > > "area range" and "area filter-list" do not affect LSAs 1 or 2, they
> > affect
> > > LSA 3. You can argue this is semantics if you want, but in binary there
> > are
> > > only two values, TRUE and FALSE.
> > >
> > >
> > >
> > > Brian McGahan, CCIE #8593 (R&S/SP/Security)
> > > bmcgahan_at_INE.com<mailto:bmcgahan_at_INE.com>
> > >
> > > Internetwork Expert, Inc.
> > > http://www.INE.com
> > >
> > > On Jan 3, 2013, at 3:25 AM, "Narbik Kocharians" <narbikk_at_gmail.com
> > <mailto:
> > > narbikk_at_gmail.com>> wrote:
> > >
> > > Unbelievable,
> > >
> > > You are saying that LSA Type-2s don't provide reachability
> information, I
> > > am saying and showing you that they do provide the subnet mask, you
> then
> > > say that you should NOT say LSA filtering because we can not
> > theoretically
> > > filter LSAs, especially when you are going to take the CCIE lab, let me
> > > tell you something, they will probably say "LSA Type 3 Filtering" as
> the
> > > header, they mention that in every Doc CD i have read, now whose
> > student/s
> > > will miss out on the terminology? You guys use it because it is
> "commonly
> > > used" (Based on Petr) or Cisco says it that way in their DOC-CD, but
> if I
> > > say it, you claim that I do not understand basics of OSPF or routing
> and
> > I
> > > should be teaching CCNA.
> > >
> > > Then, you agree with Paul about my explanation, and then you ask him
> what
> > > does that have to do with "Area range" or the other commands, so why is
> > it
> > > OK with you to use the term "LSA Filtering" and Not anyone else? Check
> > how
> > > quick you agreed with Paul, and he was basically repeating what I
> > > mentioned, that tells me that you are agreeing with me but you like to
> > > argue. I even said at the end of my post "I am not disagreeing with
> you",
> > > but I guess it did not click.
> > >
> > > Once again, stop doing that. Do you know how to unsubscribe a person
> from
> > > a thread? You are very good with google, try it one more time.
> > >
> > > On Thu, Jan 3, 2013 at 1:04 AM, Brian McGahan <bmcgahan_at_ine.com
> <mailto:
> > > bmcgahan_at_ine.com>> wrote:
> > > You need to relax Narbik. I'm not sure how you made this leap in the
> > > discussion, but thanks for once again ruining a potentially helpful and
> > > intellectual thread on the list. My apologies if I somehow offended
> you.
> > >
> > >
> > >
> > > On Jan 3, 2013, at 2:34 AM, "Narbik Kocharians" <narbikk_at_gmail.com
> > <mailto:
> > > narbikk_at_gmail.com>> wrote:
> > >
> > > You are VERY WRONG. Picking words and acting as though you are an
> > attorney
> > > did not convince me a bit, but your immaturity is what you definitely
> > > proved here today. You are in a routing loop my friend, we made a full
> > > circle.
> > >
> > > Unsubscribe me from further responses. Paul B the owner of this forum
> > > forgot to put a disclaimer about people under legal age.
> > >
> > > If this continues, I will ignore your replies or comments all together,
> > or
> > > i will be very rude.
> > >
> > > How do you connect this discussion about my students failing because in
> > > many words they attended my class? What does that have to do with this
> > > discussion? A student of mine told me that you guys in your volumes say
> > > "filtering LSA Type 3", so what gives you the right to use the terms
> that
> > > you disagree with?
> > >
> > > I even commented in your blog, when Petr wrote an article "ospf route
> > > filtering demystified" right after I released a 10 minute VoD on OSPF
> > > Filtering, and he admitted in the blog that he uses that same term
> > because
> > > Cisco uses it in their documentation, but if I use it, I don't know
> what
> > I
> > > am talking about? Here incase you forgot:
> > > http://blog.ine.com/2009/08/17/ospf-route-filtering-demystified/
> > >
> > > As I said before unsubscribe me from this thread.
> > >
> > >
> > >
> > >
> > >
> > > --
> > > Narbik Kocharians
> > > CCSI#30832, CCIE# 12410 (R&S, SP, Security)
> > > www.MicronicsTraining.com<http://www.micronicstraining.com/>
> > > Sr. Technical Instructor
> > > YES! We take Cisco Learning Credits!
> > > A Cisco Learning Partner
> > >
> > >
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> > >
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> >
> >
> >
> >
> >
> >
>
>
> --
> *Narbik Kocharians
> *CCSI#30832, CCIE# 12410 (R&S, SP, Security)
> *www.MicronicsTraining.com* <http://www.micronicstraining.com/>
> Sr. Technical Instructor
> YES! We take Cisco Learning Credits!
> A Cisco Learning Partner
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
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Received on Thu Jan 03 2013 - 22:57:29 ART