OSPF Database breakdown












Hi,

 

I have an LSA Type1
database output and I’m trying to knock sense how did some addresses are
chosen over the other.

 

OSPF Router with id(192.168.239.66) (Process ID 300)
 
                 Displaying Router Link States(Area 0.0.0.0)
 
  Link ID       ADV Router    Age        Seq#     Checksum  Link count
172.16.21.6   172.16.21.6    1731    0x80002CFB    0x69BC       8
172.16.21.5   172.16.21.5    1112    0x800009D2    0xA2B8       5
172.16.1.2    172.16.1.2     1662    0x80000A98    0x4CB6       9
172.16.1.1    172.16.1.1     1115    0x800009B6    0x5F2C       1
172.16.1.5    172.16.1.5     1691    0x80002BC     0x2A1A       5
172.16.65.6   172.16.65.6    1395    0x80001947    0xEEE1       4
172.16.241.5  172.16.241.5   1161    0x8000007C    0x7C70       1
172.16.27.6   172.16.27.6    1723    0x80000548    0x8641       4
172.16.70.6   172.16.70.6    1485    0x80000B97    0xEB84       6

 

 

Link ID: is this also the router-id? Is this address usually similar to
‘ADV Router’? If there is multiple links in the same area, how was
it chosen?

Link count: Is this the total no. of inf
detected in this area or the total no. of inf on this router inregardless of
area?

 

 

Kelvin





Comments

  • <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">





    There is one LSA-1 per router.  Inside the LSA-1 it describes the
    neighbors that router is adjacent with, along with any stub networks. 
    Look at the "show ip ospf database router 172.16.21.6" output and
    you'll see the detail inside what it's advertising.



    Brian McGahan, CCIE #8593 (R&S/SP/Security)

    [email protected]

     

    Internetwork Expert, Inc.

    http://www.InternetworkExpert.com

    Toll Free: 877-224-8987 x 705

    Outside US: 775-826-4344 x 705

    Online Community: http://www.IEOC.com

    CCIE Blog: http://blog.internetworkexpert.com






    Kelvinyeo wrote:


    Hi,

     

    I have an
    LSA Type1
    database output and I’m trying to knock sense how did some addresses
    are
    chosen over the other.

     

    OSPF Router with id(192.168.239.66) (Process ID 300)
     
                     Displaying Router Link States(Area 0.0.0.0)
     
      Link ID       ADV Router    Age        Seq#     Checksum  Link count
    172.16.21.6   172.16.21.6    1731    0x80002CFB    0x69BC       8
    172.16.21.5   172.16.21.5    1112    0x800009D2    0xA2B8       5
    172.16.1.2    172.16.1.2     1662    0x80000A98    0x4CB6       9
    172.16.1.1    172.16.1.1     1115    0x800009B6    0x5F2C       1
    172.16.1.5    172.16.1.5     1691    0x80002BC     0x2A1A       5
    172.16.65.6   172.16.65.6    1395    0x80001947    0xEEE1       4
    172.16.241.5  172.16.241.5   1161    0x8000007C    0x7C70       1
    172.16.27.6   172.16.27.6    1723    0x80000548    0x8641       4
    172.16.70.6   172.16.70.6    1485    0x80000B97    0xEB84       6

     

     

    Link ID: is this also the router-id? Is this
    address usually similar to
    ‘ADV Router’? If there is multiple links in the same area, how was
    it chosen?

    Link count: Is
    this the total no. of inf
    detected in this area or the total no. of inf on this router
    inregardless of
    area?

     

     

    Kelvin








    Internetwork Expert - The Industry Leader in CCIE Preparation

    http://www.internetworkexpert.com



    Subscription information may be found at:

    http://www.ieoc.com/forums/ForumSubscriptions.aspx

  • When you type "show ip ospf database" you will see various sections in the database output. The section you showed lists the Router LSAs for Area 0 as Brian McGahan noted.

    You will also see Net Link States (LSA Type 2), Summary Net Link States (LSA Type 3), and other sections depending on whether the router is in a stub area, nssa area, is an Area Border Router (will have database for more than one area), etc.













  • I was just listening
    to your ATC and you were the speaker..cool

     

    "show ip ospf database router 172.16.21.6" indeed
    explains on the ‘Link count’. Therefore we can conclude that this
    is the total no. of inf detected within the same area.

     

    But how about the ‘Link ID’? Is this also the
    router-id? Is this address usually similar to ‘ADV Router’? If
    there is multiple links in the same area, how was it chosen?

     

      Link ID       ADV Router    Age        Seq#     Checksum  Link count
    172.16.21.6   172.16.21.6    1731    0x80002CFB    0x69BC       8

     

     

     

    Kelvin

     







    From:
    [email protected] [mailto:[email protected]] On Behalf Of
    Brian McGahan

    Sent: 19 January 2009 01:23

    To: [email protected]

    Subject: Re: [CCIE R&S
    General] OSPF Database breakdown

     

    There is one LSA-1 per router.  Inside the LSA-1 it describes the
    neighbors that router is adjacent with, along with any stub networks. 
    Look at the "show ip ospf database router 172.16.21.6" output and
    you'll see the detail inside what it's advertising.



    Brian McGahan, CCIE #8593 (R&S/SP/Security)

    [email protected]

     

    Internetwork Expert, Inc.

    http://www.InternetworkExpert.com

    Toll Free: 877-224-8987 x 705

    Outside US: 775-826-4344 x 705

    Online Community: http://www.IEOC.com

    CCIE Blog: http://blog.internetworkexpert.com





    Kelvinyeo wrote:

    Hi,

     

    I have an LSA Type1
    database output and I’m trying to knock sense how did some addresses are
    chosen over the other.

     

    OSPF Router with id(192.168.239.66) (Process ID 300)
     
                     Displaying Router Link States(Area 0.0.0.0)
     
      Link ID       ADV Router    Age        Seq#     Checksum  Link count
    172.16.21.6   172.16.21.6    1731    0x80002CFB    0x69BC       8
    172.16.21.5   172.16.21.5    1112    0x800009D2    0xA2B8       5
    172.16.1.2    172.16.1.2     1662    0x80000A98    0x4CB6       9
    172.16.1.1    172.16.1.1     1115    0x800009B6    0x5F2C       1
    172.16.1.5    172.16.1.5     1691    0x80002BC     0x2A1A       5
    172.16.65.6   172.16.65.6    1395    0x80001947    0xEEE1       4
    172.16.241.5  172.16.241.5   1161    0x8000007C    0x7C70       1
    172.16.27.6   172.16.27.6    1723    0x80000548    0x8641       4
    172.16.70.6   172.16.70.6    1485    0x80000B97    0xEB84       6

     

     

    Link ID: is this also the router-id? Is this address usually similar to
    ‘ADV Router’? If there is multiple links in the same area, how was
    it chosen?

    Link count: Is this the total no. of inf
    detected in this area or the total no. of inf on this router inregardless of
    area?

     

     

    Kelvin







    Internetwork Expert - The Industry Leader in CCIE Preparation

    http://www.internetworkexpert.com



    Subscription information may be found at:

    http://www.ieoc.com/forums/ForumSubscriptions.aspx







    Internetwork Expert - The Industry Leader in CCIE Preparation

    http://www.internetworkexpert.com



    Subscription information may be found at:

    http://www.ieoc.com/forums/ForumSubscriptions.aspx

    No
    virus found in this incoming message.

    Checked by AVG - http://www.avg.com

    Version: 8.0.176 / Virus Database: 270.10.8/1899 - Release Date: 1/17/2009 5:50
    PM





  • <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">





    Do you have access to the CCIE R&S Open Lecture Series?  There's a
    session on "Understanding the OSPF Database" that I ran a few weeks ago
    that goes into all of this in detail.





    Brian McGahan, CCIE #8593 (R&S/SP/Security)

    [email protected]

     

    Internetwork Expert, Inc.

    http://www.InternetworkExpert.com

    Toll Free: 877-224-8987 x 705

    Outside US: 775-826-4344 x 705

    Online Community: http://www.IEOC.com

    CCIE Blog: http://blog.internetworkexpert.com






    Kelvinyeo wrote:


    I was
    just listening
    to your ATC and you were the speaker..cool

     

    "show ip ospf database
    router 172.16.21.6" indeed
    explains on the ‘Link count’. Therefore we can conclude that this
    is the total no. of inf detected within the same area.

     

    But how about the ‘Link
    ID’? Is this also the
    router-id? Is this address usually similar to ‘ADV Router’? If
    there is multiple links in the same area, how was it chosen?

     

      Link ID       ADV Router    Age        Seq#     Checksum  Link count
    172.16.21.6   172.16.21.6    1731    0x80002CFB    0x69BC       8

     

     

     

    Kelvin

     



    From:
    [email protected] [mailto:[email protected]] On Behalf Of
    Brian McGahan

    Sent: 19 January 2009
    01:23

    To:
    [email protected]

    Subject: Re: [CCIE
    R&S
    General] OSPF Database breakdown

     

    There is one LSA-1 per router.  Inside the
    LSA-1 it describes the
    neighbors that router is adjacent with, along with any stub networks. 
    Look at the "show ip ospf database router 172.16.21.6" output and
    you'll see the detail inside what it's advertising.



    Brian McGahan, CCIE #8593 (R&S/SP/Security)

    [email protected]

     

    Internetwork Expert, Inc.

    http://www.InternetworkExpert.com

    Toll Free: 877-224-8987 x 705

    Outside US: 775-826-4344 x 705

    Online Community: http://www.IEOC.com

    CCIE Blog: http://blog.internetworkexpert.com





    Kelvinyeo wrote:

    Hi,

     

    I have an
    LSA Type1
    database output and I’m trying to knock sense how did some addresses
    are
    chosen over the other.

     

    OSPF Router with id(192.168.239.66) (Process ID 300)
     
                     Displaying Router Link States(Area 0.0.0.0)
     
      Link ID       ADV Router    Age        Seq#     Checksum  Link count
    172.16.21.6   172.16.21.6    1731    0x80002CFB    0x69BC       8
    172.16.21.5   172.16.21.5    1112    0x800009D2    0xA2B8       5
    172.16.1.2    172.16.1.2     1662    0x80000A98    0x4CB6       9
    172.16.1.1    172.16.1.1     1115    0x800009B6    0x5F2C       1
    172.16.1.5    172.16.1.5     1691    0x80002BC     0x2A1A       5
    172.16.65.6   172.16.65.6    1395    0x80001947    0xEEE1       4
    172.16.241.5  172.16.241.5   1161    0x8000007C    0x7C70       1
    172.16.27.6   172.16.27.6    1723    0x80000548    0x8641       4
    172.16.70.6   172.16.70.6    1485    0x80000B97    0xEB84       6

     

     

    Link ID: is this also the router-id? Is this
    address usually similar to
    ‘ADV Router’? If there is multiple links in the same area, how was
    it chosen?

    Link count: Is
    this the total no. of inf
    detected in this area or the total no. of inf on this router
    inregardless of
    area?

     

     

    Kelvin







    Internetwork Expert - The Industry Leader in CCIE Preparation

    http://www.internetworkexpert.com



    Subscription information may be found at:

    http://www.ieoc.com/forums/ForumSubscriptions.aspx







    Internetwork Expert - The Industry Leader in CCIE Preparation

    http://www.internetworkexpert.com



    Subscription information may be found at:

    http://www.ieoc.com/forums/ForumSubscriptions.aspx

    No
    virus found in this incoming message.

    Checked by AVG - http://www.avg.com

    Version: 8.0.176 / Virus Database: 270.10.8/1899 - Release Date:
    1/17/2009 5:50
    PM








    Internetwork Expert - The Industry Leader in CCIE Preparation

    http://www.internetworkexpert.com



    Subscription information may be found at:

    http://www.ieoc.com/forums/ForumSubscriptions.aspx

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