Description

BFD is flapping between Qfx10002 and F5 devices

 

 

 

 

Symptoms

The BFD is flapping between qfx10002 and F5 device

 

From the var log we noticed the below log messages

 

%DAEMON-4-BFDD_STATE_UP_TO_DOWN: BFD Session X.X.X.X (IFL XXX) state Up -> Down LD/RD(48/2723) Up time:4d 03:23 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.

Solution

  • The Leaf is connected with F5 in ESI LAG
  • BFD is enabled for BGP, and it's experiencing flapping issues.
  • Upon reviewing the configuration, we noticed that the BFD timer is set to 200ms.
  • After checking the relevant documentation, configured BFD timer is not supported on this interface. As per the guidelines, the recommended BFD timer should be set to 1000ms.

 

For large-scale network deployments with a large number of BFD sessions, specify a minimum interval of no less than 500 ms. An interval of 1000 ms is recommended to avoid any instability issues.

 

https://www.juniper.net/documentation/us/en/software/junos/high-availability/topics/topic-map/bfd.html#:~:text=An%20interval%20of%201000%20ms,for%20Routing%20Engine%2Dbased%20sessions.

 

We need to change the BFD timer as 1000ms and check the BFD status, if the issue remains the same after change the timer, we need to check the BFD traces.

Modification History

2024-09-24 : Article Created