Routing Configuration Guide, Cisco Catalyst SD-WAN Releases 17.x

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BFD protocol for Cisco SD-WAN

Updated: February 6, 2026

Overview

Explains how Bidirectional forwarding detection (BFD) enables rapid detection of link, device, and path failures in enterprise networks, helping ensure faster recovery and high availability for critical applications.

A Bi-directional Forwarding Detection (BFD) is a network protocol that

  • detects failures rapidly between forwarding engines,

  • operates with low overhead, and

  • enables faster reconvergence of business-critical applications.

BFD provides a single, standardized method to detect link, device, or protocol failures across any layer and media.

BFD in enterprise networks

In enterprise networks, organizations increasingly run business-critical applications on a shared IP infrastructure. They design these networks with high redundancy to protect data and ensure reliability. However, redundancy works effectively only when network devices detect failures and switch to alternate paths quickly.

Traditional protocols often take more than a second to identify failures, which delays recovery for time-sensitive applications. BFD solves this problem by detecting failures rapidly and triggering faster recovery, allowing networks to maintain consistent performance and uptime.

How BFD works in Cisco Catalyst SD-WAN

With this feature, the Cisco Catalyst SD-WAN solution includes two independent BFD types that operate separately without conflict.

BFD Support for Cisco Catalyst SD-WAN Routing Protocols (Legacy BFD): This legacy BFD feature already exists in Cisco IOS XE and extends to the Cisco Catalyst SD-WAN solution starting from Cisco IOS XE Catalyst SD-WAN Release 17.3.1a.

Cisco Catalyst SD-WAN BFD: This feature specifically supports overlay BFD, which already exists in the Cisco Catalyst SD-WAN solution.

This type of BFD detects failures in the overlay tunnel and has these characteristics:

  • It operates by default and cannot be disabled.

  • It typically runs for the Cisco Catalyst SD-WAN Overlay Management Protocol (OMP).

  • In addition to detecting link failures, Cisco Catalyst SD-WAN BFD measures latency, loss, jitter, and other link statistics that application-aware routing uses.

Table 1. Differences: BFD for Cisco Catalyst SD-WAN routing protocols versus Cisco Catalyst SD-WAN BFD
BFD for Cisco Catalyst SD-WAN routing protocols Cisco Catalyst SD-WAN BFD

  • Runs on both, transport-side and service-side interfaces

  • The following protocols can be registered: BGP, OSPF, and EIGRP

    • BGP (transport and service side

    • EIGRP (service side)

    • OSPF and OSPFv3 (service side)

  • Detects link failures for peers in terms of whether a peer is up or down

  • Runs on a Cisco Catalyst SD-WAN tunnel to detect failures in the overlay tunnel

  • Is enabled by default and cannot be disabled

  • Is typically enabled for OMP

  • Besides link failures, it also measures latency, loss, and other link statistics used by application-aware routing

As shown in the image, you configure BFD for a routing protocol through Cisco SD-WAN Manager. Cisco SD-WAN Manager then pushes this configuration to the edge router. In this example, OSPF receives forwarding path detection failure messages from BFD. When a physical link fails, BFD notifies OSPF, prompting it to shut down its neighbors and withdraw or restore any routing information exchanged with remote neighbors.

Similarly, Edge 1 connects to the internet router through its transport interface. You configure BFD for BGP between the transport side of Edge 1 and the internet router. In this setup, BFD monitors the connection’s health and reports any detected failures.

Supported protocols and interfaces

Supported protocols

In Cisco Catalyst SD-WAN, the following routing protocols can receive forwarding-path failure notifications from BFD:

  • BGP

  • EIGRP

  • OSPF

  • OSPFv3

Supported interfaces

BFD supports the following interface types:

  • GigabitEthernet

  • TenGigabitEthernet

  • FiveGigabitEthernet

  • FortyGigabitEthernet

  • HundredGigabitEthernet

  • SVIs

  • Subinterfaces

Restrictions for Cisco IOS XE Catalyst SD-WAN devices in controller mode

  • The device supports only single-hop BFD.

  • The device does not support BFD for static routes.

  • To change the BFD session mode between software and hardware, you must remove all existing BFD configurations and reconfigure them.

  • The device supports BFD only for BGP, EIGRP, OSPF, and OSPFv3.

  • Cisco SD-WAN Manager cannot monitor BFD for routing protocols in Cisco Catalyst SD-WAN; you must use CLI show commands for monitoring.

  • After a BFD session is established, the device does not update BFD session modes (echo-no-echo or software- hardware) immediately when you change BFD template parameters in Cisco SD-WAN Manager; it applies the change only after the session flaps at least once.