Rip timers

Anthony Sequiera's post on study strategy reminded me to look over RIP. One bit of confusion here. The command reference for RIP says this about the invalid timer:

 


Interval of time (in seconds) after which a route is declared invalid; it should be at least three times the value of the
update argument. A route becomes invalid when there is an absence of updates that refresh the route. The route then enters into a holddown state. The route is marked inaccessible and advertised as unreachable. However, the route is still used for forwarding packets. The default is 180 seconds.

 

So I understand this as after the invalid timer expires, the route is placed into holddown. THEN the route is in the holddown state waiting for that timer to expire before an alternate path is used. Problem is, Vol 1 (v4.1) RIP shows the timers for invalid and holdown as both 3 to meet the convergence time of 5 seconds. In that case, I see those 2 timers as running parallel. And seeing as they are both default of 180, is that the case?


 

The Doc CD has a habit of wording documentation in a way that seems to go against configurations I view in the WB's. So parallel or in sequence with these timers?

Comments

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    The timers run in parallel, but it's not clear from the documentation
    example.  The invalid timer is what makes the route go "possibly down"
    in the routing table.  When holddown occurs you can't accept an update
    about the prefix with a worse metric.  Normally you invalidate the
    route and go into holddown at the same time, but you technically don't
    have to.  The flush timer is what controls when it actually leaves the
    routing table. 



    Look at the IEWB-RS Volume 1 Version 5 section on RIP for some more
    detail on this.





    HTH,



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

    [email protected]

     

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    luisgarcia wrote:


    Anthony Sequiera's post on study strategy reminded me to look
    over RIP. One bit of confusion here. The command reference for RIP says
    this about the invalid timer:

     


    Interval of time (in seconds) after which a
    route is declared invalid; it should be at least three times the value
    of the
    update argument. A route becomes invalid when there is an absence of
    updates that refresh the route. The route then enters

    into a holddown state. The route is marked inaccessible and advertised as
    unreachable. However, the route is still used for forwarding packets.
    The default is 180 seconds.

     

    So I understand this as after the invalid timer expires, the
    route is placed into holddown. THEN the route is in the holddown state
    waiting for that timer to expire before an alternate path is used.
    Problem is, Vol 1 (v4.1) RIP shows the timers for invalid and holdown
    as both 3 to meet the convergence time of 5 seconds. In that case, I
    see those 2 timers as running parallel. And seeing as they are both
    default of 180, is that the case?

     

    The Doc CD has a habit of wording documentation in a way that
    seems to go against configurations I view in the WB's. So parallel or
    in sequence with these timers?







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