MicroBFD flap were seen on multiple routers at same time where timer is set to 5x30ms.
No interface flap.
Log Snippet:
Oct 20 01:34:02 2024 xxxx bfdd[30016]: BFDD_STATE_UP_TO_DOWN: BFD Session 172.26.13.2 (IFL 221) state Up -> Down LD/RD(1606/950) Up time:9w2d 23:11 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
Oct 20 01:34:02 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 1606, new state: down, interface: et-4/0/24, peer addr: 172.26.13.2
Oct 20 01:34:02 2024 xxxx bfdd[30016]: BFDD_STATE_UP_TO_DOWN: BFD Session 172.26.13.2 (IFL 200) state Up -> Down LD/RD(1608/952) Up time:9w2d 23:11 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
Oct 20 01:34:02 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 1608, new state: down, interface: et-4/0/1, peer addr: 172.26.13.2
Oct 20 01:34:02 2024 xxxx bfdd[30016]: BFDD_STATE_UP_TO_DOWN: BFD Session 172.26.13.2 (IFL 199) state Up -> Down LD/RD(1598/949) Up time:9w2d 23:11 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
Oct 20 01:34:02 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 1598, new state: down, interface: et-4/0/0, peer addr: 172.26.13.2
Oct 20 01:34:02 2024 xxxx bfdd[30016]: BFDD_STATE_UP_TO_DOWN: BFD Session 172.26.13.2 (IFL 222) state Up -> Down LD/RD(1612/953) Up time:9w2d 23:11 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
Oct 20 01:34:02 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 1612, new state: down, interface: et-4/0/25, peer addr: 172.26.13.2
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_UP: local discriminator: 1606, new state: up, interface: et-4/0/24, peer addr: 172.26.13.2
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_UP: local discriminator: 1608, new state: up, interface: et-4/0/1, peer addr: 172.26.13.2
Oct 20 01:34:03 2024 xxxx 2bfdd[30016]: BFDD_TRAP_SHOP_STATE_UP: local discriminator: 1612, new state: up, interface: et-4/0/25, peer addr: 172.26.13.2
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_UP: local discriminator: 1598, new state: up, interface: et-4/0/0, peer addr: 172.26.13.2
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_STATE_UP_TO_DOWN: BFD Session 172.26.13.3 (IFL 190) state Up -> Down LD/RD(1841/1720) Up time:2w4d 22:43 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 1841, new state: down, interface: et-3/0/19, peer addr: 172.26.13.3
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_STATE_UP_TO_DOWN: BFD Session 172.26.13.3 (IFL 178) state Up -> Down LD/RD(1861/1735) Up time:2w0d 07:12 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 1861, new state: down, interface: et-3/0/7, peer addr: 172.26.13.3
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_STATE_UP_TO_DOWN: BFD Session 172.26.13.3 (IFL 177) state Up -> Down LD/RD(1839/1716) Up time:2w4d 22:43 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 1839, new state: down, interface: et-3/0/6, peer addr: 172.26.13.3
Oct 20 01:34:03 2024 xxxx bfdd[30016]: BFDD_STATE_UP_TO_DOWN: BFD Session 172.26.13.3 (IFL 189) state Up -> Down LD/RD(1844/1721) Up time:2w4d 22:43 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
The MicroBFD runs in Distributed mode (i,e Ukern thread in linecards), so 10ms interval looks to be to too aggressive, recommend to use 3x300ms.