Hardware Support For Bfd - Cisco Catalyst 4500 Series Configuration Manual

Chapter 37 Configuring Bidirection Forwarding Detection
If you use fast hellos for either BGP or OSPF, this Interior Gateway Protocol (IGP) protocol reduces its
failure detection mechanism to a minimum of one second.
Advantages to implementing BFD over reduced timer mechanisms for routing protocols include the
following:
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Hardware Support for BFD

The Catalyst 4500 supports a limited number of BFD sessions in hardware. Placing a session in BFD
hardware is termed hardware offload. The advantage of hardware offload is that session keep-alive is
handled entirely in hardware, placing no load on the CPU.
Not all BFD sessions can be offloaded to hardware. The requirements for offloaded sessions are:
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The number of offloaded sessions varies by supervisor. For WS-X45-SUP6-E, WS-X45-SUP6L-E,
WS-X4948-E, and C4900M, the number of offloaded sessions is 63.
The show bfd neighbor detail command displays print statistics for software and hardware (offloaded)
sessions. Hardware sessions provide a limited set of statistics. In particular, statistics for packet transmit
and receive intervals are not available for hardware sessions.
The holddown and hello counts are zero for all offloaded sessions.
Hardware offload is not supported for IPv6 BFD sessions.
Note
How to Configure Bidirectional Forwarding Detection
Support on the Catalyst 4500E is limited. Starting with Cisco IOS Release IOS 15.1(1)SG, Bidirectional
Note
Forwarding Detection (BFD) is supported only on Catalyst 4900M, and Catalyst 4948E Ethernet
switches.
You start a BFD process by configuring BFD on the interface. When the BFD process is started, no
entries are created in the adjacency database; in other words, no BFD control packets are sent or
received. BFD echo mode, which is supported in BFD Version 1 for Cisco IOS Release 15.1(1)SG, is
enabled by default. BFD echo packets are sent and received, in addition to BFD control packets. The
adjacency creation takes places once you have configured BFD support for the applicable routing
protocols. This section contains the following procedures:
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OL-25340-01
Although reducing the EIGRP, BGP, and OSPF timers can result in minimum detection timer of one
to two seconds, BFD can provide failure detection in less than one second.
Because BFD is not tied to any particular routing protocol, it can be used as a generic and consistent
failure detection mechanism for EIGRP, BGP, and OSPF.
Because some parts of BFD can be distributed to the data plane, it can be less CPU-intensive than
the reduced EIGRP, BGP, and OSPF timers, which exist wholly at the control plane.
BFD version 1
IPv4
No echo mode
Configuring BFD Session Parameters on the Interface, page 37-8
How to Configure Bidirectional Forwarding Detection
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
(required)
37-7