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  • 1.  BFD flap

    Posted 06-01-2023 23:08

    I have the following :

    Anyone can shed some light on what Control Detection Time Expired ? it seems the timestamp does not show any delay.
    thanks !!


  • 2.  RE: BFD flap

    Posted 06-02-2023 06:24

    Assuming you are seeing bfd flapping when you don't think there is an actual link issue, the general source would be a too low test interval for the bfd configuration and increasing the time would get the bfd check settle.



    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
    http://puluka.com/home
    ------------------------------



  • 3.  RE: BFD flap

    Posted 06-02-2023 10:59

    thanks so much !!

    But I need to find the proof for the detection interval configured is too low. From the above, the timestamp for the packets in and out is within the the interval configured, why Control Detection time expired ?




  • 4.  RE: BFD flap

    Posted 06-03-2023 07:04

    Sorry, don't know that specific answer.  When we encountered flapping we simply increased the interval by 100 at a time until it settled on what was good for the particular circumstances.

    From practical experience I can say that intervals lower than 300 never worked. 

    And that on a number of links we had to raise the interval to as high as 1000 to prevent flapping.  These tended to be long fiber runs in the real world running many km on poles.



    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
    http://puluka.com/home
    ------------------------------



  • 5.  RE: BFD flap

    Posted 06-04-2023 14:58

    thanks so much!

    The reason why I like to find the root cause is the current time interval used to work. So sth unknown occurs. We need to provide any reason to make any change. As the BFD timer change will affect the failover timing.