In IOS, yes. It's not a widely standard behavior though.
-- Marko Milivojevic - CCIE #18427 (SP R&S) Senior CCIE Instructor - IPexpert On Fri, Jan 4, 2013 at 10:32 AM, Carlos G Mendioroz <tron_at_huapi.ba.ar> wrote: > Something that popped to my mind when I read this is a hidden gotcha in IOS > regarding type-3 LSAs going across areas. > > May be you know already, but it is worth bringing it back: when an ABR > copies a T3 from area 0 to a non area 0, it does a RIB check to see if the > route is actually in there. If it is not, the T3 is not copied. > It works just like if you were redistributing OSPF(A0) into OSPF(Ax). > > -Carlos > > Marko Milivojevic @ 04/01/2013 06:44 -0300 dixit: > >> LSA summarization is not done in/from the RIB. Original Type-3 is created >> from the computed SPF tree, which in turn is based on the information from >> Type 1 and Type 2 LSAs. "The routing table structure" in the context quoted >> is what I called the "computed SPF tree", not the RIB, as the RFC has no >> control over how RIB is constructed. >> >> -- >> 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 4, 2013, at 1:20, shiran guez <shiranp3_at_gmail.com> wrote: >> >>> Hi All >>> >>> I have to agree with Brian and add some to back it up: >>> >>> 1) LSA type 1 or LSA type 2 does not need to be filtered or summarized >>> simply because that are locally significant to the area that they where >>> generated >>> RFC2328 >>> " >>> >>> 12.4.1. Router-LSAs >>> >>> ... >>> >>> The LSA is flooded throughout the particular area, and no further. >>> >>> ... >>> >>> 12.4.2. Network-LSAs >>> >>> ... >>> >>> The network-LSA is flooded throughout the area that contains the >>> transit network, and no further. >>> >>> " >>> >>> 2) LSA type 3 is generated from the RIB using the SPF algorithm >>> >>> "12.4.3. Summary-LSAs >>> >>> ... >>> >>> The precise summary routes to advertise into an area are >>> determined by examining the routing table structure (see >>> Section 11) in accordance with the algorithm described >>> below. >>> >>> " >>> >>> >>> - Any filtering and / or summary is done on the RIB not on the >>> database >>> it self! >>> >>> Personal Note: I much prefer the semantics story being told. if you wish >>> to >>> follow someone all your professorial life you can take the easy way and >>> learn configurations and some of the basic or even advanced designs and >>> you >>> will do fine in your work, however if you wish to be followed upon and be >>> that one that people turn to for answers, you MUST know and understand >>> the >>> semantics even if it mean that you need to waist more time and effort. >>> >>> >>> >>> >>> On Thu, Jan 3, 2013 at 11:46 AM, 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 >>>> >>>> _______________________________________________________________________ >>>> Subscription information may be found at: >>>> http://www.groupstudy.com/list/CCIELab.html >>> >>> >>> >>> -- >>> Shiran Guez >>> MCSE CCNP NCE1 JNCIA-ENT JNCIS-ENT CCIE #20572 >>> http://cciep3.blogspot.com >>> http://www.linkedin.com/in/cciep3 >>> http://twitter.com/cciep3 >>> >>> >>> Blogs and organic groups at http://www.ccie.net >>> >>> _______________________________________________________________________ >>> Subscription information may be found at: >>> http://www.groupstudy.com/list/CCIELab.html >> >> >> >> Blogs and organic groups at http://www.ccie.net >> >> _______________________________________________________________________ >> Subscription information may be found at: >> http://www.groupstudy.com/list/CCIELab.html >> >> >> >> >> >> >> > > -- > Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina Blogs and organic groups at http://www.ccie.netReceived on Fri Jan 04 2013 - 11:41:59 ART
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