hold down timer on interface

Created: Sep 18, 2019 06:59:44Latest reply: Sep 20, 2019 01:18:41 100 5 0 0
  Rewarded Hi-coins: 0 (problem resolved)

can anyone explain me , what is the default value of down timer on Giga interface & how to change this timer to reduce the network flapping if transmission have a delay.? and any other alternative solution?

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Popeye_Wang
Admin Created Sep 18, 2019 07:20:44 Helpful(0) Helpful(0)

DO you mean the response hold time of the system after an interface goes Down?
By default, the response hold time of the system after an interface goes Down is 0 ms. That is, the system responds immediately after an interface goes Down.
On some device, like NE router, you can use the carrier down-hold-time command to change the time.


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Popeye_Wang
Popeye_Wang Admin Created Sep 18, 2019 07:20:44 Helpful(0) Helpful(0)

DO you mean the response hold time of the system after an interface goes Down?
By default, the response hold time of the system after an interface goes Down is 0 ms. That is, the system responds immediately after an interface goes Down.
On some device, like NE router, you can use the carrier down-hold-time command to change the time.


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LSA
LSA Created Sep 18, 2019 18:55:48 Helpful(0) Helpful(0)

Posted by Popeye_Wang at 2019-09-18 07:20 DO you mean the response hold time of the system after an interface goes Down?By default, the respon ...
Thanks @Popeye_Wang for reply...yes response hold time as carrier down hold time used for avoid flapping...but we can also used BFD for detection...can you clarify ...these two BFD and down hold time...
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Popeye_Wang
Popeye_Wang Admin Created Sep 19, 2019 07:38:14 Helpful(0) Helpful(0)

Posted by LSA at 2019-09-18 18:55 Thanks @Popeye_Wang for reply...yes response hold time as carrier down hold time used for avoid fl ...
I think this is two completely different mechanisms. You can set hold time to a larger value to avoid frequent route changes caused by link flapping. (To prevent the device from responding quickly to interface status changes.)
And the BFD function is used to quickly detect link faults and enable the device to respond quickly.
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LSA
LSA Created Sep 19, 2019 10:13:50
Thanks @Popeye_Wang..but i think the flapping is also fault. then BFD not detect flapping? @chenhui can you share obeservation on this please. Thanks  
chenhui
chenhui Admin Created Sep 20, 2019 01:18:41 Helpful(0) Helpful(0)

@LSA hi,
as you and @Popeye_Wang said, BFD cannot detect flapping, actually, BFD is not designed to detect the link flapping.
Imagine a scenario that two routers interconnected to each other with other layer 2 switches between them, and the BFD is enabled, the transmission interval of the BFD detection packet is 2 seconds. If the link flapping occurs just following the success of last BFD detection. and the link flapping duration time is less than 2 seconds. In this scenario, the BFD wouldn't detect the link down, but the link down does really occurred.

Hold down timer is a delay, the devices wouldn't take any actions during this period after the interface turn down.
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