Link Detection Debounce Timer

The link debounce timer avoids frequent updates (churn) to higher layer protocols during flapping of an interface. The initial link state is UP. The link goes DOWN. If the Link comes UP and goes DOWN, The link DOWN AND link UP timer is started and being restarted on each flap (link comes up and goes down again). For each link DOWN, link down timer will start and it restarts on flap within the link debounce interval. For each link UP, link up timer will start and it restarts on flap within the link debounce interval.

Keep the following in mind when using the Link detection debounce timer:

  • Link debounce timer is supported only for physical L2 and L3 interfaces.
  • When debounce timer is configured we won't be able to configure the link-debounce-timer config and viceversa.
  • The link debounce flap-count refers to the number of flaps OcNOS receives while the debounce timer is running:
    • The flap-count is only updated if the timer is still running and OcNOS receives a link status event for the interface.
    • The flap-count is reset at the subsequent start of the link debounce timer.
  • Protocol-specific timers such as BFD which depend on the link status should be configured to minimum of 1.5 times the value of the link-debounce time. Otherwise it could affect the protocol states if the link debounce timer is still running.
  • Protocols such as PO, OSPF, BFD, ISIS, BGP which depends on the link status, in this case we should ensure on both the connected interfaces we need to configure the link-debounce timer.
  • The debounce timer must be configured on both ends of the network link.
  • Enabling the debounce timer delays the detection of link up and down status, resulting in traffic loss during that period and impacting the convergence of some protocols.

Topology

Figure 57. Link detection debounce timer topology

Configuration

RTR1

#configure terminal

Enter configure mode.

(config)#interface xe1

Enter interface mode

(config-if)#link-debounce-time 4000 5000

Configure link-debounce-time where link-up timer is 4000 ms and link-down timer is 5000 ms

(config-if)#commit

Commit the candidate configuration to the running configuration

(config-if)#exit

Exit interface mode

RTR2

#configure terminal

Enter configure mode.

(config)#interface xe1

Enter interface mode.

(config-if)#link-debounce-time 4000 5000

Configure link-debounce-time where link-up timer is 4000 ms and link-down timer is 5000 ms

(config-if)#commit

Commit the candidate configuration to the running configuration.

(config-if)#exit

Exit interface mode.

Validation

Copy 
#show interface xe1 | i Debounce Link Debounce timer: enable
    Linkup Debounce time 4000 ms Linkdown Debounce time 5000 ms
    Linkup Debounce status : idle
    Linkdown Debounce status : idle

RTR1 and RTR2 outputs after interface flap:

Copy 
#show interface xe1 | i debounce Link Debounce timer: enable
Linkup Debounce time 4000 ms Linkdown Debounce time 5000 ms
Flap Count: 1
Last Debounce Flap :    
Linkup Debounce status : idle
Linkdown Debounce status : idle
 
#show interface xe1 | i debounce 
  Link Debounce timer: enable
    Linkup Debounce time 4000 ms Linkdown Debounce time 5000 ms
    Flap Count: 1
    Last Debounce Flap :    Linkup Debounce status : idle
 Linkdown Debounce status : idle