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[MX] Micro BFD sessions between Juniper and Cisco routers not coming up

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This article describes a common cause for micro BFD sessions to fail to establish between Cisco and Juniper routers, and suggests a solution for the same.



After enabling micro BFD sessions on a link aggregation group (LAG) between Cisco and Juniper devices, the micro BFD sessions are not coming up. This may cause the associated LAG interface to be marked as down. Observe the following session on a router that is running Junos OS. The remote state is shown as "AdminDown" here:

user@host> show bfd session detail
                                                  Detect   Transmit
Address                  State     Interface      Time     Interval  Multiplier             Down      et-0/1/0       0.000     1.000        3  
 Client LACPD, TX interval 0.050, RX interval 0.050
Local diagnostic None, remote diagnostic None
Remote state AdminDown, version 1    <<< remote AdminDown
 Session type: Micro BFD             <<< session type is Micro BFD


  • On Cisco routers, there are two modes for micro BFD sessions: cisco mode and ietf mode. By default, these sessions are set to cisco mode.

  • A micro BFD session will establish between Cisco and Juniper routers only if the mode on the Cisco router is configured as ietf.



The solution is to manually configure the micro BFD session mode as "ietf" on Cisco routers. As per Cisco documentation, the micro BFD session mode can be configured at both the global and interface levels.


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