Managing and Tracing BFD Sessions During Unified ISSU Procedures
Bidirectional Forwarding Detection (BFD) sessions temporarily increase their detection and transmission timers during unified ISSU procedures. After the upgrade, these timers revert to the values in use before the unified ISSU started. The BFD process replicates the unified ISSU state and timer values to the backup Routing Engine for each session.
No additional configuration is necessary to enable unified
ISSU for BFD. However, you can disable the BFD timer negotiation during
the unified ISSU by including the no-issu-timer-negotiation statement at the [edit protocols bfd] hierarchy level.
[edit protocols bfd] no-issu-timer-negotiation;
If you include this statement, the BFD timers maintain their original values during unified ISSU.
The BFD sessions might flap during unified ISSU or Routing Engine switchover, depending on the detection intervals.
For more information about BFD, see the Junos OS Routing Protocols Library.
To configure unified ISSU trace options for BFD sessions,
include the issu statement at the [edit protocols
bfd traceoptions flag] hierarchy level.
[edit protocols]
bfd {
traceoptions {
flag issu;
}
}