# Bidirectional Forwarding Detection (BFD) Configuration Module

This configuration module configures the basic BFD ([RFC5880](https://datatracker.ietf.org/doc/html/rfc5880)) parameters. To configure fast failover with BFD, use the routing protocol [configuration modules](../module-reference.md). At the moment you can use BFD with  [IS-IS](isis.md) and [OSPF](ospf.md).

(bfd-platform)=
BFD is supported on these platforms:

| Operating system      | Configurable<br>timers | OSPF | IS-IS |
| --------------------- | :-: | :-: | :-: |
| Arista EOS            | ✅  | ✅  | ✅  |
| Aruba AOS-CX          | ✅  | ✅  |  ❌  |
| Cisco IOS             | ✅  | ✅  | ✅  |
| Cisco IOS XE          | ✅  | ✅  | ✅  |
| Cisco Nexus OS        | ✅  | ✅  | ✅  |
| Cumulus Linux         | ✅❗| ✅  |  ❌  |
| FRR                   | ✅❗| ✅  |  ❌  |
| Dell OS10             |  ❌  | ✅  |  ❌  |
| Juniper vMX           | ✅❗| ✅  | ✅  |
| Juniper vPTX          | ✅❗| ✅  | ✅  |
| Juniper vSRX 3.0      | ✅❗| ✅  | ✅  |
| Mikrotik RouterOS 6   |  ❌  | ✅  | ✅  |
| Mikrotik RouterOS 7   |  ❌  |  ❌  |  ❌  |
| Nokia SR Linux        | ✅  | ✅  | ✅  |
| Nokia SR OS           | ✅  | ✅  | ✅  |
| VyOS                  | ✅❗| ✅  | ✅  |

**Notes:**
* Cumulus Linux and FRR configure BFD as part of OSPFv2/OSPFv3 configuration.
* Junos configuration template configures BFD timers within routing protocol configuration, not in individual interfaces
* VyOS configuration template configures BFD timers only at global level

## Parameters

The following parameters can be set globally or per node/link:

* **min_tx**: The desired minimal interval for sending BFD packets, in msec.
* **min_rx**: The required minimal interval for receiving BFD packets, in msec
* **min_echo_rx**: Echo function timer, in msec
* **multiplier**: Number of missed packets before the session is considered down

Global defaults are set pretty high to accommodate a wide range of virtual network devices with varying quality of BFD implementation:

* **min_tx**: 1 second (1000 msec)
* **min_rx**: 1 second (1000 msec)
* **min_echo_rx**: disabled (set to zero)
* **multiplier**: 3

Valid intervals and ranges are platform-dependent. Some platforms have lower default values:

| platform | min-tx    | min-rx   |
|----------|-----------|----------|
| nxos     | 1000 msec | 500 msec |
| srlinux  | 100 msec  | 100 msec |
| sros     | 100 msec  | 100 msec |

## Example

To enable BFD using default values on all IS-IS interfaces:

```
module: [ isis, bfd ]

isis:
 bfd:
  ipv4: True
  ipv6: True
```