OSPF - IBGP peering with non backbone router.

sunny81sunny81 Registered Users Posts: 7 ■□□□□□□□□□
I am preparing in JNCIP-M.
I feel bit of confusion in the JNCIP book on OSPF as IGP part.
From the book, only required to include interface lo0 into OSPF configuration at backbone /area 0.
For the sub-area, there is no inclusive of lo0 in OSPF configuration.

It caused when i building the IBGP and and peering with those sub-area IGP's loopback add, cannot established the peering. i have to configure lo0 into OSPF only peering is up.

Any expert here could clarify it?


  • hoogen82hoogen82 Member Posts: 272
    I am assuming it is introduction of loopback as type 3 in backbone and the rest would be type 1... there is no way they would have told not to include the loopback under OSPF
    IS-IS Sleeps.
    BGP peers are quiet.
    Something must be wrong.
  • zoidbergzoidberg Member Posts: 365 ■■■■□□□□□□
    if i still have any memory left....

    back in the day, loopback was automatically advertised into ospf. 8.4? 8.5? that changed and you need to specify it.
  • zoidbergzoidberg Member Posts: 365 ■■■■□□□□□□
    from 8.5 release notes

    OSPF link-state advertisements—Beginning with JUNOS Release 8.5, OSPF no longer advertises a router identifier interface that is not configured to run OSPF as a stub network in its link-state advertisements. [Routing Protocols]

    so, back when the book was written, if you used your loopback as the router-id, it was automatically advertised into ospf. i think if you used the router-id command, and that id was different that the loopback ip, then you had to add the loopback to ospf to have it advertise.
  • zoidbergzoidberg Member Posts: 365 ■■■■□□□□□□
    JUNOS Enterprise Routing, Page 89

    To paraphrase...
    JUNOS would automatically advertise a stub route to the router-id interface, so you didn't need to run an IGP on your loopback. 8.5 onward, you need to enable OSPF on the loopback if you want to advertise it in OSPF.
  • sunny81sunny81 Registered Users Posts: 7 ■□□□□□□□□□
    No wonder, i am using 9.4 and 9.5 machines to practice.
    What version will be using in exam? 8.5?
  • zoidbergzoidberg Member Posts: 365 ■■■■□□□□□□
    i don't recall what the M was.... 8.1 maybe? ER was 8.4, i think. could be completely different now, both of these values are subject to change at any time. by the time the new labs launch i would expect the code to be drastically different and hopefully a bit recent :)

    the exams do not really focus on code related features, but i guess you will need to be prepared for changes in behavior like this. when you register for an exam, i believe they tell you what code is being used. if not, you can ask. you could even just ask now. either i asked, or they told me during registration, one way i knew what i was walking into.

    thankfully, study material like the ER book mentioned issues like this change in ospf behavior.
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