Configuring BFD for OSPF

After BFD for OSPF is enabled, when a link fails, the device rapidly detects the failure, notifies the OSPF process or interface of the fault, and instructs OSPF to recalculate routes. This speeds up OSPF network convergence.

Prerequisites

Before configuring BFD for OSPF, complete the following task:

Configuring IP addresses for interfaces to ensure that neighboring routers are reachable at the network layer.
Establishing the OSPF Neighbor Relationship.

Context

After BFD for OSPF is configured, when detecting a link fault, BFD rapidly notifies the routers on both ends of the link of the fault, triggering rapid OSPF convergence. When the OSPF neighbor relationship goes Down, the BFD session will be dynamically deleted.

Before configuring BFD for OSPF, enable BFD globally.

Perform the following steps on the FWs between which a BFD session is to be created.

Procedure

Access the system view.
```
system-view
```
Enable BFD.
```
bfd
```
Return to the system view.
```
quit
```
Access the OSPF process view.
```
ospf [ process-id ]
```
Configure BFD for OSPF.
```
bfd all-interfaces enable
```
The default parameter values are used to create a BFD session.

If all the interfaces in a certain process are configured with BFD and their neighbor relationships are in the Full state, OSPF creates BFD sessions with default parameter values on all the interfaces in the process.
(Optional) Set BFD session parameters.
```
bfd all-interfaces { min-rx-interval receive-interval | min-tx-interval transmit-interval | detect-multiplier multiplier-value | frr-binding  } ^*
```
You can skip this step. The default interval at which BFD packets are transmitted and the default detection multiplier are recommended.

The parameters are configured based on the network status and network reliability requirements. A short interval at which BFD packets are transmitted can be configured for a link that has a higher requirement for reliability. A long interval at which BFD packets are transmitted can be configured for a link that has a lower requirement for reliability.
- Actual interval at which BFD packets are transmitted on the local router = Max { configured interval transmit-interval at which BFD packets are transmitted on the local router, configured interval receive-interval at which BFD packets are received on the peer router }
- Actual interval at which BFD packets are received on the local router = Max { configured interval transmit-interval at which BFD packets are transmitted on the peer router, configured interval receive-interval at which BFD packets are received on the local router }
- Actual time for detecting BFD packets = Actual interval at which BFD packets are received on the local router x Configured detection multiplier multiplier-value on the peer router
For example:
- On the local router, the configured interval at which BFD packets are transmitted is 200 ms; the configured interval at which BFD packets are received is 300 ms; the detection multiplier is 4.
- On the peer router, the configured interval at which BFD packets are transmitted is 100 ms; the interval at which BFD packets are received is 600 ms; the detection multiplier is 5.
Then:
- On the local router, the actual interval at which BFD packets are transmitted is 600 ms calculated by using the formula max {200 ms, 600 ms}; the interval at which BFD packets are received is 300 ms calculated by using the formula max {100 ms, 300 ms}; the detection period is 1500 ms calculated by multiplying 300 ms by 5.
- On the peer router, the actual interval at which BFD packets are transmitted is 300 ms calculated by using the formula max {100 ms, 300 ms}, the actual interval at which BFD packets are received is 600 ms calculated by using the formula max {200 ms, 600 ms}, and the detection period is 2400 ms calculated by multiplying 600 ms by 4.
(Optional) Prevent an interface from dynamically creating a BFD session.
After BFD for OSPF is configured, all interfaces on which neighbor relationships are Full in the OSPF process will create BFD sessions. To prevent specific interfaces from being enabled with BFD, disable these interfaces from dynamically creating BFD sessions.
1. Return to the system view.
```
quit
```
2. Access the interface view.
```
interface interface-type interface-number
```
3. Prevent the interface from dynamically creating a BFD session.
```
ospf bfd block
```