Lab03 - Notes on ALL Tasks

Sorry guys, but I don't have the time to create a topic per task, so here goes:

(*) Task 4.2: configure MD5 auth in the correct order to avoid getting bizzaroid results... ;-)

(*) Task 4.5: the Virtual-Link between R1 and R3 does NOT go up, unless we configure at least an interface in Area 0, on R1 or on R3 ( e.g. put lo0 in Area0 then remove it from Area 0 => the VL goes & stays up; else nothing happens) This won't survie a reload of the router(s). Seems to be an IOS-dependent behaviour.

(*) Task 5.1: it's a simple sync/blackhole problem on R5, just redistribute BGP->OSPF on R3 and BGP->EIGRP on R6; why the route-maps w/ AS_PATH filtering in the solution, why ^254_ and ^54_ ? Some sort of best practice ?!?



  • 4.5) Agreed, hence I choose to advertise R3's Lo0 into Area 0 rather than the area 3 solution. VL doesn't have a hello/dead timers unless explicitly configured, that's why it will not survive a reload or clear ip ospf process.

    5.1) Correct, but you'll confuse the IGP this way. The IGP routes will seem to be reachable via both R3 and R6. However, you want to insure that AS 254 is reachable via R3 and AS 54 is reachable via 54.
  • Correction:

    5.1) Correct, but you'll confuse the IGP this way. The BGP routes will seem to be reachable via both R3 and R6. However, you want to insure that AS 254 is reachable via R3 and AS 54 is reachable via R6.
  • RE: 4.5,

    how do you stop R1 and R5 from seeing R3-L0 as /32 once the VL is up, if you put that interface into Area0? the area 0 range command will summerize to /24 for R4, but not the others.

    and Re:4.9 soln..

    would you not need to "passive-interface L0" in router rip? task 4.1 states that updates should ONLY be sent out interfaces included in "RIPv2" on the diagram. just adding network allows rip updates out L0... which is not on the diagram!

    (i know the update really goes nowhere, but isn't the passive a requirement to keep task 4.1 true?)
  • OSPF treats a loopback interface as a "host" (/32) route by default. Use "ip ospf network point-to-point" in the loopback interface configuration mode to advertise the subnet.

  • darrell,

    task states "do not use the ip ospf network-type point-to-point" for this.
  • Sorry - I didn't look at the WB before replying. I will have to think about a solution some more...

  • RE: 4.5

    By putting the Loopback into an new area (area 3 in the SG) and using the area range command, it's summarized and R1 & R5 only see the summary.

    RE: 4.9

    I would put passive-interface default on the RIP and only allow it on the serial interface per the diagram. The SG will be updated to reflect this, I think it's a valid point.

  • thanks for the reply, steve...

    the problem I had with the SG solution was the VL never came up, since there is no area 0 on either R3 or R1. doing the trick described above of adding an area 0, then removing it works... but it will not survive a reload.

    what is the trick to getting a VL to activate with no area 0 on either router, let alone in the whole ospf domain?

    thanks again!
  • That's a good question. After reading it I went and read from the RFC on OSPF to get a better understanding of virtual-links. According the RFC, a virtual-link can only be enabled on two routers with an interface in the backbone area. I've updated the SG to reflect this. You have to have an interface in Area 0 for the virtual-link to come up.

  • Steve Schoeneman indicates that "passive int lo0" should be added to SG. Have not seen this update.

    Id doesn't seem necessary to me, but I am not the expert.
    So passive ? or not passive ?

    I confirmation would be appreciated.
  • Hello ,

    Sorry for my question, I did not test the lab yet by my hand, but while I'm reading it I can't understand why we need redistribution between the BGP and the IGP , I may missed something here , but I can see that there is IGP between the BB routers and the Internal network , and full IGP redistribtion , so all the IGP routes should be advertised already to the BB routs

    and the BGP routes is advertised via the BGP to the internal network !!!!

    where is the exact point that weneed redistribution from the BGP to the IGP ??

  • Hi,
    Just to confirm,Bullet 1 of Task 4.6 creates Area0!
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