On Junos Evolved PTX10K platforms, Bidirectional Forwarding Detection (BFD) protocol sessions will flap continuously and never become stable after this. This exposure is not deterministic and is only exposed if BFD is operating in distributed or inline mode.
In the distributed or inline mode, BFD sessions run on the ASIC firmware. The Routing Engine creates BFD sessions and passes them to the ASIC firmware for processing.
Example configuration:
BFD for OSPF (single-hop distribute BFD):
set protocols ospf area <area-id> interface <int name> bfd-liveness-detection minimum-interval <interval time>
set protocols ospf area <area-id> interface <int name> bfd-liveness-detection multiplier <multiplier value>
BFD session transitions from Down to Init to UP and then:
<DATE> <Router Name> bfdd[16473]: BFDD_STATE_UP_TO_DOWN: BFD Session <IP> (IFL 13217) state Up -> Down LD/RD(170/16404) Up time:00:00:07 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
<DATE> Received Downstream AdjDown (22) len 32:<DATE> IfIndex (3) len 4: 13217
<DATE> DistributionHandle (21) len 4: 0x32990
<DATE> Discriminator (63) len 4: 0xaa
<DATE> Session <IP> (IFL 13217) state Up -> Down Up time:00:00:07 Local reason: CtlExpire Remote reason: None local discr = 170 remote discr = 16404 tx :50000 rx :50000
Use the below commands to check the BFD session status.
"show ppm control protocol bfd session"
"show bfd session”
External-Trigger
This issue might be seen if the following conditions are met:
* On Junos Evolved PTX10K platforms
* BFD is operating in hardware-assisted inline mode
Example here show BGP BFD flap continuously:
user@router> show bfd session address 10.0.0.2 extensive
Jul 07 13:21:24
Detect Transmit
Address State Interface Time Interval Multiplier
10.0.0.2 Init et-0/0/0.100 6.000 2.000 3
Client BGP, TX interval 0.200, RX interval 0.200
Session down time 00:00:19, previous up time 00:00:03
Local diagnostic CtlExpire, remote diagnostic None
Remote state Down, version 1
Session type: Single hop BFD
Min async interval 0.200, min slow interval 2.000
Adaptive async TX interval 2.000, RX interval 2.000
Local min TX interval 2.000, minimum RX interval 0.200, multiplier 3
Remote min TX interval 2.000, min RX interval 2.000, multiplier 3
Local discriminator 177, remote discriminator 1090543937
Echo TX interval 2.000, echo detection interval 6.000
Echo mode disabled/inactiveno-absorb, no-refresh
Session ID: 430
1 sessions, 1 clients
Cumulative transmit rate 0.5 pps, cumulative receive rate 0.5 pps
Jul 07 13:21:27
10.0.0.2 Up et-0/0/0.100 6.000 2.000 3
Session up time 00:00:03, previous down time 00:00:19
Local diagnostic None, remote diagnostic None
Remote state Up, version 1
Remote min TX interval 0.050, min RX interval 0.050, multiplier 3
Echo mode disabled/inactive
Jul 07 13:21:28
Session down time 00:00:00, previous up time 00:00:04
Local diagnostic CtlExpire, remote diagnostic NbrSignal
Issue is addressed in PR1822526.
Introduced-In-Releases
23.2R1EVO
Resolved-In
evo:23.2R2-S3-EVO evo:23.4R2-S3-EVO evo:24.2R1-S2-EVO evo:24.2R2-EVO evo:24.4R1-EVO evo:25.1R1-EVO evo:26.3R1-EVO junos:24.2R2 junos:24.4R1 junos:25.1R1
Workaround: Router reboot may fix this issue temporarily.