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S5720-HI BFD unstable when BFD number is more than seventeen

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Hello everyone,

Today, I will introduce how to handle the problem that BFD is unstable on the S5720-HI when the number of BFD sessions is greater than 17.

Issue Description

On S5720-32C-HI-24S-AC, to achieve the recovery time within the required 50ms, currently, 17 BFD sessions are configured for VRRP and it working fine. As soon as customers configure another BFD session for newly added Vlanif all the BFD sessions start flapping randomly.

Alarm Information

Apr 4 2018 17:27:48+03:00 ICC-LAN-UP-1 D/4/STACHG_TODWN(l)[49]:BFD session changed to Down. (SlotNumber=0, Discriminator=8197, Diagnostic=DetectDown, Applications=VRRP | AUTO, ProcessPST=False, BindInterfaceName=Vlanif166, InterfacePhysicalState=Up, InterfaceProtocolState=Up)

Apr  4 2018 17:27:48+03:00 ICC-LAN-UP-1 D/4/STACHG_TOUP(l)[50]:BFD session changed to Up. (SlotNumber=0, Discriminator=8197, FormerStatus=Down, Applications=VRRP | AUTO, BindInterfaceName=Vlanif166, ProcessPST=False)

Apr 4 2018 17:27:48+03:00 ICC-LAN-UP-1 D/4/STACHG_TODWN(l)[51]:BFD session changed to Down. (SlotNumber=0, Discriminator=8210, Diagnostic=DetectDown, Applications=VRRP | AUTO, ProcessPST=False, BindInterfaceName=Vlanif15, InterfacePhysicalState=Up, InterfaceProtocolState=Up)

Apr 4 2018 17:27:48+03:00 ICC-LAN-UP-1 D/4/STACHG_TOUP(l)[52]:BFD session changed to Up. (SlotNumber=0, Discriminator=8210, FormerStatus=Down, Applications=VRRP | AUTO, BindInterfaceName=Vlanif15, ProcessPST=False)

Handling Process

1. The customer's need is that the recovery time should be within 50ms.

2. The number of the BFD session is more than seventeen when the issue happens.

3. Checking the configuration, "set service-mode enhanced" doesn't configure.

Root Cause

On S5720-Hi, BFD process by software. If you want that the VRRP recovery time should be within 50ms, you need to add the command "set service-mode enhanced ", with this command BFD is processed by the hardware.


<HUAWEI> system-view

[HUAWEI] set service-mode enhanced

Warning: This command will affect forward performance. Continue? [Y/N]:y

That is all I want to share with you! Thank you!

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