BFD

In this section:

  1. Bidirectional Forwarding Detection Overview
    Bidirectional Forwarding Detection (BFD) is a lightweight hello protocol, with little system overhead, used to rapidly detect link faults without overloading the system. BFD improves network performance by using hardware acceleration for sending packets, resulting in less overheard on the control CPU. BFD works by checking that a device is alive, thus providing rapid detection of the failure of a forwarding path and minimizing traffic loss. BFD can detect the failure of the forwarding plane in a sub-second time interval that is user-configurable.
  2. BFD Session States
    The following are states through which a BFD session can move:
  3. BFD in a Stacking System
    The configuration of a BFD session occurs on the unit where the TX port, or next hop, resides. The TX port is known once the ARP, or the next hop in the case of a multihop BFD session, is resolved.
  4. BFD High Availability Support
    BFD is deployed in the stacking setup where units take up active, standby, and member roles, as illustrated in the following figure. When a failover occurs and the active unit fails or goes through a switchover, the standby unit takes over as active. Therefore, BFD-enabled routes are available for forwarding both during and post switchover.
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  6. BFD Session Configuration Where Next Hop is a VE Interface
    BFD session configurations in the micro controller use only a local port number as the TX port parameter. When the TX port, or next hop, for the BFD session is part of a VE interface with a physical port, the session is configured on one port for the VLAN. ARP resolution for the peer allocates the actual outgoing port to use.
  7. BFD Session Configuration Where Next Hop is a LAG Interface
  8. BFD Considerations and Limitations
    Consider the following when configuring BFD:
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  10. BFD Support for OSPF
    BFD support for OSPFv2 and OSPFv3 can be configured so that OSPF is a registered protocol with BFD. When BFD support for OSPF is configured, forwarding path detection failure messages are received from BFD. BFD sessions can rapidly detect link faults and notify OSPF so that it quickly responds to network topology changes. BFD support for OSPF is disabled by default.
  11. BFD Support for BGP
    BFD support for BGP4 and BGP4+ can be configured so that BGP is a registered protocol with BFD, and forwarding path detection failure messages are received from BFD. BFD for BGP is disabled by default. When BFD support for BGP is enabled, BFD rapidly detects faults on links between BGP peers and reports faults to BGP. BFD for BGP is supported for both single-hop and multi-hop iBGP and eBGP sessions with IPv4 or IPv6 neighbors. BFD for BGP is supported for both the default VRF and nondefault VRF instances.
  12. BFD for Static Routes
    Unlike routing protocols such as OSPF and BGP, static routing has no method of fault detection or peer discovery. BFD for IPv4 and IPv6 static routes provides rapid detection of failure in the bidirectional forwarding path between BFD peers.
  13. BFD Configuration Examples
  14. Displaying BFD Information
    Various show commands can display statistical information about BFD configurations.