Configuring BFD Hardware Offload
Bidirectional Forwarding Detection (BFD) offload support provides the functionality to offload a BFD session to the hardware. BFD is a forwarding path failure detection protocol and reduces the overall network convergence time by sending rapid failure detection packets (messages) to the routing protocols for recalculating the routing table. Previously the performance of BFD was restricted to the capabilities of CPU and IOS on the switch. Effective failure detection requires BFD to run at high frequencies (using aggressive timers as low as 50ms), which was not possible because of CPU and IOS restrictions.
For information on configuring BFD see Configuring BFD section of ME 3800x and ME 3600x Switches Software Configuration Guide.
Table 6-1 Supported Hardware for BFD Hardware Offload
ME-3600X-24CX Series Switch
Restrictions for BFD Hardware Offload Support
- Only BFD version 1 is supported.
- Only FPGA offloaded BFD sessions are supported on Cisco ME 3600X-24CX-M.
- The switch supports BFD only in Asynchronous mode or no echo mode.
- The switch supports 511 asynchronous BFD sessions.
- BFD hardware offload is supported for IPv4 sessions with non-echo mode only.
- BFD hardware offload is supported on port-channel interfaces.
- BFD hardware offload is supported only for the ethernet interface.
- BFD hardware offload is not supported for IPv6 BFD sessions.
- BFD hardware offload is not supported for BFD with TE/FRR.
- If the no echo command is executed when the session is up, use the shut/no shut command to offload BFD in hardware.
Configuring BFD Hardware Offload Support
By default the Cisco IOS runs in echo mode. Hence, BFD is not offloaded to the hardware until the no bfd echo command is executed. The no bfd echo command changes the mode from "echo" to "Asynchronous".
ip address 10.1.1.6 255.255.255.0
bfd interval 50 min_rx 50 multiplier 3
Note To enable BFD Hardware Offloading on all interfaces, enable the no bfd echo command on all interfaces.
Verifying BFD Hardware Offload Support
Ensure that the Session host value displays "Hardware". Use the show bfd neighbors detail to verify the configuration of BFD Hardware Offload. Hardware BFD sessions have a LD of 1-511.
Note Sometimes if BFD session is brought up after the registered protocol is up, the session may come up in Software. Shut down the interface and apply the BFD configuration to ensure that session comes back up in Hardware (Session Host: Hardware as shown below).
Switch# show bfd neighbours details
NeighAddr LD/RD RH/RS State Int
220.127.116.11 1/11 Up Up Vl3336
Session state is UP and not using echo function.
Local Diag: 0, Demand mode: 0, Poll bit: 0
MinTxInt: 50000, MinRxInt: 50000, Multiplier: 3
Received MinRxInt: 100000, Received Multiplier: 3
Holddown (hits): 0(0), Hello (hits): 100(0)
Elapsed time watermarks: 0 0 (last: 0)
Registered protocols: ISIS CEF OSPF
Last packet: Version: 1 - Diagnostic: 0
State bit: Up - Demand bit: 0
Poll bit: 0 - Final bit: 0
Multiplier: 3 - Length: 24
My Discr.: 11 - Your Discr.: 294
Min tx interval: 100000 - Min rx interval: 100000
Min Echo interval: 0 ould