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BGP flap on qfx5100 with BFD configured when running 'request support information'

  [KB34061] Show Article Properties


Summary:

QFX5100 has a hardware limitation with the number of PPM adjacencies.  This number is variable depending on the switch load.  When there is over 20 PPM adjacencies, the switch is at risk.

Symptoms:

When running a RSI, the PPM will drop BFD hello packets. Then the BGP session will drop.

Cause:
root@lab-switch> start shell
root@lab-switch:RE:0% vty fpc0
FPC0(lab-switch vty)# sh ppm adjacencies

PPM distributed adjacencies

Protocol   Holdtime (msec) PPM handle  Inline

BFD        3000            7           No
BFD        3000            8           No
LACP       3000            17          No
LACP       3000            21          No
LACP       3000            22          No
LACP       3000            18          No
LACP       3000            19          No
LACP       3000            20          No

Total adjacencies: 8    <-- at risk if this number is 20 or higher
Solution:

This is a product/hardware limitation.  You can either lower the PPM adjacencies, or raise the BFD timer.  You can also deactivate BFD, then collect the RSI.

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