Configuring Static BFD for IS-IS

BFD can provide link fault detection featuring light load and high speed (within milliseconds). Static BFD needs to be configured.

Usage Scenario

On IS-IS networks, IS-IS neighbors periodically send Hello packets to detect neighbor status changes. For networks that require fast convergence and zero packet loss, IS-IS is unreliable to detect link faults. To address this issue, configure BFD for IS-IS.

BFD includes static BFD and dynamic BFD. Static BFD is easy to control and flexible to deploy. To save memory and ensure the reliability of key links, implement BFD on these links. Static BFD helps detect link faults rapidly and implement fast route convergence.

To configure a static BFD session, you need to manually configure BFD session parameters, including the local and remote discriminators.

BFD detects only the one-hop link between IS-IS neighbors because IS-IS establishes only one-hop neighbors.

Procedure

Run system-view
The system view is displayed.
Run bfd
Global BFD is enabled on the local end.
Run quit
Return to the system view.
(Optional) To configure BFD session check for an IS-IS process, perform the following steps:
1. Run isis [ process-id ]
  The IS-IS view is displayed.
2. Run bfd session-up check
  BFD session check is configured for the IS-IS process.
When the Layer 2 network is running normally, IS-IS neighbor relationships can be established and routes can be delivered. However, if the Layer 3 network is unreachable, upper-layer traffic loss occurs. To resolve this problem, configure BFD session check for an IS-IS process by running the bfd session-up check command. This ensures that an IS-IS neighbor relationship is established only when the BFD session is up on corresponding interfaces. After this function is configured, it applies only to the neighbor relationships to be established (it does not apply to existing neighbor relationships).
Run interface interface-type interface-number
The interface view is displayed.

BFD can be enabled on physical interfaces only.
Run isis bfd static
Static BFD is enabled on the interface.
Run quit
Return to the system view.
Run bfd session-name bind peer-ip ip-address [ interface { interface-name | interface-type interface-number } ]
A BFD session is bound to an interface.

If both peer-ip (IP address of the peer end) and interface (local interface) are specified, BFD only monitors a single-hop link with interface as the outbound interface and peer-ip as the next hop address.
Run the following commands as required:
- To set the local discriminator, run the discriminator local discr-value command.
- To set the remote discriminator, run the discriminator remote discr-value command.
The local discriminator of the local device must be the same as the remote discriminator of the peer device, and the remote discriminator of the local device must be the same as the local discriminator of the peer device.
Run commit
The configuration is committed.

Checking the Configurations

Run the following commands to check the previous configuration.

Run the display isis bfd [ process-id | vpn-instance vpn-instance-name ] session { peer ip-address | all } command to view the information about the BFD session.
Run the display isis interface verbose command to view the configurations of BFD for IS-IS on an interface.