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Notable Replies

  1. system says:

    Rene ! this is really grt !

  2. system says:

    Hi, thank you very much for this very easy to understand explanation. Great job rene.

  3. Hi Jurati,

    Yes this is possible, when your OSPF neighbor adjacency is working over the frame relay link you should be able to configure a virtual link.

    Rene

  4. Hi John,

    Good question, the only other option where you can set the DNA bit is the "on demand circuit". This can be used for (WAN) links where you pay for a certain amount of bytes of per minute/second. You don't want to refresh LSAs on these links since they will keep the link up.

    I guess that's why they also decided to set the DNA bit for the virtual link in case you have links like this.

    Rene

  5. Dear Andrew P

    Many thanks for your quick repsonse.
    I am not sure you understood my question correctly so hopefully this will help as below to clarify :-

    R5
    Area 3
    ONLY
    NO SUMMARIZATION
    
    |
    |
    |
    |

    R4
    Area 1 (+ 3)
    ABR
    SUMMARIZATION
    OF AREA 3 ONLY
    (VL end point
    for area 3) 
    
    | 
    |                           
    |
    |

    R3
    Area 1
    ONLY 
    NO SUMMMARIZATION
    (VL Transit Router)
    
    |
    |
    |

    R1     -----------------  R2       -----------  R6     ---------------  R7   -------------------- R8
    Area 0                    Area 0 (+ 1 + 2)      Area 2                  Area 2 (+ 5)              Area 5
    ONLY                      ABR                   ONLY                    ABR                       ONLY
    NO SUMMMARIZATION         SUMMARIZATION >       NO SUMMARIZATION        SUMMARIZATION >           NO SUMMARIZATION
                              OF BOTH AREA 1 + 2                            OF AREA 5 ONLY
                              (VL Origin Points x 2                         (VL End Point
                              to reach Area 3 + 5)                          for area 5)

    R1# sh ip route ospf | include IA : showed summaries (/16) for Area 1, 2, 3 + 5

    R5# sh ip route ospf | include IA : showed summaries (/16) for Area 1, 2 + 5

    R8# sh ip route ospf | include IA : showed summaries (/16) for Area 1, 2 + 3

    ===================================================================================================================

    Main Points:
    
    > Area 0 DIRECTLY interconnects two areas, area's 1 + 2 via its ABR
    > VL's configured on this ABR to interconnect area 3 (using transit area 1) and to interconnect area 5 (using transit area 2)
    > summarisation on ABR's as follows:-
     >> R2 (area 0 main ABR adjoining area's 1 + 2) - summarises area 1 + 2 subnets
     >> R4 (area 1 + 3 ABR) - summarises area 3 subnets
     >> R7 (area 2 + 5 ABR) - summarises area 5 subnets

    My Question:

    Am I summarising on the correct area's on the relevant (correct) ABR's ?

    Many Thanks
    Will V

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