Re: LSA Type 4 again

From: Mohamed El Henawy <m.henawy_at_link.net>
Date: Mon, 7 Sep 2009 00:27:31 +0300

Yupe...Thanks a lot :)

if these kinds of questions in the open ended....I don't know if it will be
fair or not...too tricky ...at the end the route reached the last hop router
and we know that Type7 to 5 conversion happened..what else we need

the question I always think about is to which level of details we need to
study ( I don't mean in particular this example but in general ) ...10 days
to find the answer for my question
  ----- Original Message -----
  From: Narbik Kocharians
  To: Mohamed El Henawy
  Cc: Molomo ; Rick Mur ; ccielab_at_groupstudy.com
  Sent: Monday, September 07, 2009 1:15 AM
  Subject: Re: LSA Type 4 again

  Perfect. Do you see now how it works?

  On Sun, Sep 6, 2009 at 2:12 PM, Mohamed El Henawy <m.henawy_at_link.net>
wrote:

    i did it

    output from R1 when Area 1 is normal area

                OSPF Router with ID (10.10.10.10) (Process ID 1)

                    Summary ASB Link States (Area 0)

      Routing Bit Set on this LSA
      LS age: 46
      Options: (No TOS-capability, DC, Upward)
      LS Type: Summary Links(AS Boundary Router)
      Link State ID: 22.22.22.22 (AS Boundary Router address) ===> R3
      Advertising Router: 1.1.1.1
      LS Seq Number: 80000001
      Checksum: 0x6F6F
      Length: 28
      Network Mask: /0
            TOS: 0 Metric: 1

    output when Area 1 is NSSA

                OSPF Router with ID (10.10.10.10) (Process ID 1)

      ----- Original Message -----
      From: Narbik Kocharians
      To: Mohamed El Henawy
      Cc: Molomo ; Rick Mur ; ccielab_at_groupstudy.com
      Sent: Monday, September 07, 2009 12:07 AM
      Subject: Re: LSA Type 4 again

      It will be easy to lab it up.

      R1 ------ Area 0 ------ R2 ------ Area 1 ------- R3

      Set area 1 to nssa and configure R3 to redistribute a connected
interface. Then, do a "Show ip ospf da asbr-summ" on R1. Then try it again
without having Area 1 as NSSA and see the difference.

      On Sun, Sep 6, 2009 at 1:03 PM, Mohamed El Henawy <m.henawy_at_link.net>
wrote:

        Hello Molomo ,

        can you plz share the output of the show ?

        ----- Original Message ----- From: "Molomo" <letjedilakopa_at_gmail.com>
        To: "Rick Mur" <rmur_at_ipexpert.com>
        Cc: <ccielab_at_groupstudy.com>
        Sent: Sunday, September 06, 2009 5:50 PM
        Subject: Re: LSA Type 4 again

          Rick,
          Actually I did lab it and it was not permitted,

          R1---area 1--- R2 ---area 0 --- R3 --area 0--- R4--- area 2--- R5

          area 0 backbone
          area 1 normal area
          area 2 is nssa

          R5 ASBR

          on R1 I cannot see the LSA type 4.

          Regards,
          Molomo

          On Sun, Sep 6, 2009 at 4:43 PM, Rick Mur <rmur_at_ipexpert.com> wrote:

            It could be allowed in the NSSA area, but it would have no use.
            You are correct, the ABR generates a type 4 LSA, when it sees type
5 LSA's
            indeed to describe the location of the ASBR.

            Try to lab it up. Create a topology, insert some external routes
in OSPF
            and issue a 'show ip ospf database' on a router within the NSSA
and see if
            you have a type-4 in your database. It's always good to see the
theory

          being

            confirmed in a lab, at least that is what helps me to understand
and
            remember the theory.

            --
            Regards,

            Rick Mur
            CCIE2 #21946 (R&S / Service Provider)
            Sr. Support Engineer IPexpert, Inc.
            URL: http://www.IPexpert.com <http://www.ipexpert.com/>

            On 6 sep 2009, at 16:27, Molomo wrote:

             Experts,

              Jeff Doyle says LSA type 4 is allowed in nssa area ( see table
below). I
              would have thought that since LSA 5 is not permitted then no
need to
              generate LSA 4.

              My understanding is , ABR generates LSA 4 based on the type 5,
to describe
              the position of the ASBR.

              Or am I missing something here?

              I have also seen this in Quick Reference Sheet by Anthony
Sequeira.

               Table 8-5. LSA types allowed per area type.

              Area Type

              1&2

              3

              4

              5

              7

              Backbone (area 0)

              Yes

              Yes

              Yes

              Yes

              No

              Non-backbone, non-stub

              Yes

              Yes

              Yes

              Yes

              No

              Stub

              Yes

              Yes

              No

              No

              No

              Totally stubby

              Yes

          No[*]<mk:@MSITStore:C:\Documents%20and%20Settings\user\Desktop\R&S%
20CCIE\Rec
          ommended%20Reading\Books\Cisco%20press\Jeff%20Doyle\CCIE_Profession
al_Develop
          ment_Routing_TCPIP,_Volume_I,_Second_Edition.chm::/1587052024/ch08l
ev1sec1.ht
          ml#ch08tn01>

              No

              No

              No

              Not-so-stubby

              Yes

              Yes

              Yes

              No

              Yes

              [*] Except for a single type 3 LSA per ABR, advertising the
default route

              Regards,

              Molomo

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      --
      Narbik Kocharians
      CCSI#30832, CCIE# 12410 (R&S, SP, Security)
      www.MicronicsTraining.com
      Sr. Technical Instructor

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      Checked by AVG - www.avg.com
      Version: 8.5.409 / Virus Database: 270.13.80/2349 - Release Date:
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  Narbik Kocharians
  CCSI#30832, CCIE# 12410 (R&S, SP, Security)
  www.MicronicsTraining.com
  Sr. Technical Instructor

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Received on Mon Sep 07 2009 - 00:27:31 ART

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