Vol 3 Task 4.6

Just a hint, to finish task 4.6, read task 4.8 first.

Comments

  • i had read the entire core lab from beginning to end making notes along the way, but i am still confused as to where is it mentioned to configure area 4 between r4 and r5 over the unnumbered links. does anyone have a clue or is this an oversight? pls help.

  • I will try and answer the question the best way I can. You can also post your question in the CCIE general Technical forum to get more answers, you need to add more details though since many people dont have access to the lab material when they answer the question.

    First of all the task and the do's and dont's do not prohibit you to add an Area. The Lab diagram leaves it open what area to put between R4 and R5. If you look close in the solution guide, you are not running area 4 between r4 and r5, but area 0. Area 4 consists of R4L0 alone.

    Task 4.6 wants you to inject the L0 with a mask of /24. There are 3 ways of doing this:

    See the blog from Anthony

    R/S 3.0 Configuration Options

    By Anthony Sequeira, #15626

    OSPF
    Advertising Masks for Loopbacks in OSPF
    Option 1 – OSPF network command
    Option 2 – Redistribute connected – Watch for Later Redistribution Issues
    Option 3 – Area Range command

    Option 1 and 2 are not allowed because of the wording in the task. So we need to go with option 3. Would the area range command have worked also using area 0? I don't know. If you test it out using area 0, please let me know if it worked.

  • thank you so very much for clarifying this for me. this makes total sense now. i appreciate the quick response!

    i will try it out later today with area 0 range XXXX XXXXX and will let you know if anything usual occurs, behaviors, etc.

  • Maybe I misread what was typed above, but I don't think the area 0 range command would work here.  Assuming you're using ip unnumbered with the serials similiar to the SG, then those interfaces would become part of area 0 already.  This would change R4 from an ABR into a regular OSPF enabled router in a single area, and I believe you need to be an ABR to properly use area range command. 

    As Berlin noted, the use of area 4 is completely arbitrary.

    -skint

  • If you are struggling to get R4 and R5 OSPF neighbors established, here's a hint:
    Double check your "ip unnumbered" statements on the Serial link interface between them

    using the wrong unnumbered interface could cost you plenty of time - i learnt the hard way

     

  • As long as you don't use lo0 you should be able to complete these tasks pretty easily :)

    Also, I tend to use the interface level command to enable ospf on an interface. This way, I don't have to care about making mistakes when typing IPs in.

    Eric

  • For this to work, I used the lo0 interface as the ip Unnumbered IP's for both R4 and R5....

    Note that the ppp peer neigh route will automagicly be installed in each others RIB..... Thus I've used the interface command on R5 to prohibit the peer route to be advertised from R5 to R4......


    R5

     

    interface Serial0/1/0

     ip unnumbered Loopback0

     encapsulation ppp

     ip ospf 1 area 0

     no peer neighbor-route


    and also made the serial part of Area 0...not violating any requirements....


    Then on R4... I've used the same method than SG to create a different area (area 45) and then summarise the Lo0 range to the required /24..... and advert this to R5,,,,


    O IA    150.7.4.0/24 [110/65] via 150.7.4.4, 02:38:59, Serial0/1/0


    due to the fact that I've made the serial part of area 0...there's no issue later to get the adj to form!





  • For this to work, I used the lo0 interface as the ip Unnumbered IP's for both R4 and R5....

    Note that the ppp peer neigh route will automagicly be installed in each others RIB..... Thus I've used the interface command on R5 to prohibit the peer route to be advertised from R5 to R4......

    R5

    interface Serial0/1/0

     ip unnumbered Loopback0

     encapsulation ppp

     ip ospf 1 area 0

     no peer neighbor-route


    and also made the serial part of Area 0...not violating any requirements....

    I also did the same way its meeting the task requirements without breaking lab rules.

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