Re: OSPF LSA type 3 filtering

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
>
>
> Blogs and organic groups at http://www.ccie.net
>
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Received on Thu Jan 03 2013 - 22:56:16 ART