Description

Control Expire/NbrSignal & Detect Timer Expiry/Received DOWN from PEER messages can cause BFD protocol flap.

Symptoms

From the log messages, we could see the router R1’s Local diagnostic reason shows as ControlExpire and the down reason as Detect Timer Expiry

Router R2 says it’s Local Diag as Neighbor signaled, and down Reason shows as Down from Peer. So, it is clear that, Router R1 was missing keepalives inbound. 

Messages (R1): 

R1 bfdd[2110]: BFDD_STATE_UP_TO_DOWN: BFD Session 192.168.105.209 (IFL 453) state Up -> Down LD/RD(16/38) Up time:1w6d 06:38 Local diag: CtlExpire Remote diag: None Reason: Detect Timer Expiry.
R1 bfdd[2110]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 16, new state: down, interface: ge-1/0/0.0, peer addr: 192.168.105.209
R1 rpd[2292]: RPD_OSPF_NBRDOWN: OSPF neighbor 192.168.105.209 (realm ospf-v2 ge-1/0/0.0 area 0.0.0.0) state changed from Full to Down due to InActiveTimer (event reason: BFD session timed out and neighbor was declared dead)



Messages (R2):

R2 bfdd[2106]: BFDD_STATE_UP_TO_DOWN: BFD Session 192.168.105.242 (IFL 398) state Up -> Down LD/RD(20/19) Up time:08:28:25 Local diag: NbrSignal Remote diag: CtlExpire Reason: Received DOWN from PEER.
R2 bfdd[2106]: BFDD_TRAP_SHOP_STATE_DOWN: local discriminator: 20, new state: down, interface: irb.6, peer addr: 192.168.105.242
R2 rpd[2283]: RPD_OSPF_NBRDOWN: OSPF neighbor 192.168.105.242 (realm ospf-v2 irb.6 area 0.0.0.0) state changed from Full to Down due to InActiveTimer (event reason: BFD session timed out and neighbor was declared dead)

Solution

R1 router wasn’t receiving any keepalives from the peer end router R2, which is causing the BFD protocol flap. 

Modification History

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