BFD Hardware Assist

Bidirectional Forwarding Detection (BFD) hardware assist support provides the functionality to run a BFD session in hardware. Effective failure detection requires BFD to run at high frequencies (using aggressive timers as low as 3 ms), which was not possible in the Software Mode because of CPU and EXOS restrictions.

To make BFD sessions to run in the hardware, the following configuration are required:

Hardware BFD is enabled by configuring one of the unused front panel port as a loopback port, which should not be available for switching the user data traffic. This port will be used internally by the BFD hardware to send control packets.
Ensure ipforwarding is enabled on the BFD interfaces.
Nexthop MAC of neighbor should be known for the session creation. The BFD process will trigger ARP to resolve the nexthop MAC if not configured statically.

L2 topology convergence time might affect the BFD sessions running in the lower interval.

Unconfiguring loopback on for BFD will disable the hardware assist support. Supported lowest interval is 3 ms in hardware mode.

Sample config:

Configure the port 1 as loopback port dedicated for BFD:

#configure bfd hardware-assist primary loopback-port 1

To check the number of BFD sessions supported in the hardware and configured loopback port:

#show bfd
..
.. 
Hardware Assist Operational State         : Enabled(Loopback 
port not configured) 
Hardware Assist Primary Loopback Port     : 1 
Hardware Assist Secondary Loopback Port   : None
Maximum # of Hardware Assist Sessions     : 900

To find the session running the hardware:

#show bfd session detail
Neighbor       : 10.10.10.2          Local       : 10.10.10.1          
VR-Name        : VR-Default          Interface   : v1                  
Session Type   : Single Hop          State       : Down
.. 
Hardware Assist                 : Yes

To see the hardware counters:

#show bfd counters
#show bfd session 10.10.10.2 counters

Published March 2020prev | next

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