Configuring Static BFD for IS-IS
Context
On an IS-IS network, a device periodically sends Hello packets to detect the neighbor status change. By default, the device considers a neighbor Down when it does not receive a Hello packet from the neighbor after sending three Hello packets (30 seconds). This IS-IS fault detection mechanism, however, cannot provide high reliability for the network that requires fast network convergence and no packet loss. BFD for IS-IS can solve this problem. BFD is a millisecond-level fault detection mechanism. It can fast detect faults on the link between IS-IS neighbors. Therefore, BFD can speed up IS-IS route convergence, ensures fast link switchover, and reduces traffic loss.
- Static BFD can be manually controlled and is easy to deploy. To save memory and ensure reliability of key links, BFD can be deployed on specified links.
- Establishing and deleting BFD sessions need to be manually triggered and lack flexibility. Configuration errors may occur. For example, if an incorrect local or remote discriminator is configured, a BFD session cannot work properly.
A BFD session currently does not detect route switching. If the change of bound peer IP address causes a route to switch to another link, the BFD session is negotiated again only when the original link fails.
Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support BFD for IS-IS.
Procedure
- Run system-view
The system view is displayed.
- Run bfd
BFD is enabled globally.
- Run quit
The system view is displayed.
- Run bfd cfg-name bind peer-ip ip-address [ interface interface-type interface-number ]
BFD is enabled between the specified interface and peer router.
If a peer IP address and a local interface are specified in the bfd command, BFD monitors only a single-hop link with the interface specified in the bfd command as the outbound interface and with the peer IP address specified in the peer-ip command as the next-hop address.
- Set discriminators.
Run discriminator local discr-value
A local discriminator is set.
Run discriminator remote discr-value
A remote discriminator is set.
The local discriminator of a device must be the remote discriminator of the device on the other end; otherwise, a BFD session cannot be established. In addition, the local and remote discriminators cannot be modified after being configured.
The local discriminator of the local device must be the same as the remote discriminator of the remote device, and the remote discriminator of the local device must be the same as the local discriminator of the remote device.
- Run commit
Configurations are committed.
- Run quit
The system view is displayed.
- Run interface interface-type interface-number
The view of the specified interface is displayed.
- (Optional) On an Ethernet interface, run undo portswitch
The interface is switched to Layer 3 mode.
By default, an Ethernet interface works in Layer 2 mode.
Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
- Run isis bfd static
Static IPv4 BFD is enabled on the specified interface.
Verifying the Configuration
You can check information about a BFD session only after parameters of the BFD session are configured and the BFD session is established.
Run the display isis [ process-id | vpn-instance vpn-instance-name ] bfd session { peer ip-address | all } command to check information about the BFD session.
Run the display isis interface verbose command. The command output shows that the status of static BFD for IS-IS process is Yes.