Re: OSPF LSA type 3 filtering

From: Marko Milivojevic <markom_at_ipexpert.com>
Date: Thu, 3 Jan 2013 20:01:14 -0800

The discussion was about the traditional OSPF, not when used as a PE-CE, which has slightly different architectural rules. Also, OSPF in VRF doesn't automatically become an ABR. Only un a presence of BGP, but as I said - a different topic.

Also, "capability vrf-lite" doesn't turn off setting the border bit, only ignores the downstream one.

--
Marko Milivojevic - CCIE #18427 (SP R&S)
Senior CCIE Instructor - IPexpert
:: This message was sent from a mobile device. I apologize for errors and brevity. ::
On Jan 3, 2013, at 13:57, Jose Jara <jjarafiz_at_gmail.com> wrote:
> 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:
>> http://www.groupstudy.com/list/CCIELab.html
> 
> 
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Received on Thu Jan 03 2013 - 20:01:14 ART

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