Configuring IS-IS TI-LFA FRR
This section describes how to configure IS-IS TI-LFA FRR.
Usage Scenario
With the development of networks, VoIP and on-line video services require high-quality real-time transmission. Nevertheless, if an IS-IS fault occurs, multiple processes, including fault detection, LSP update, LSP flooding, route calculation, and FIB entry delivery, must be performed to switch traffic to a new link. As a result, the traffic interruption time is longer than 50 ms, leading to a failure to satisfy real-time requirements.
TI-LFA FRR protects links and nodes on SR tunnels. If a link or node fails, traffic is rapidly switched to a backup path, minimizing traffic loss.
In some LFA or RLFA scenarios, the P space and Q space do not share nodes or have direct neighbors. If a link or node fails, no backup path can be calculated, causing traffic loss and resulting in a failure to meet reliability requirements. In this situation, TI-LFA can be used.
This function is supported only when the card interoperability mode is enhanced.
Pre-configuration Tasks
Before configuring IS-IS TI-LFA FRR, complete the following tasks:
Configure IP addresses for interfaces to implement connectivity at the network layer.
Configure basic IS-IS functions.
- Globally enable the segment routing capability.
- Enable the segment routing capability in an IS-IS process.
Procedure
- Run system-view
The system view is displayed.
- Run isis [ process-id ]
An IS-IS process is enabled, and the IS-IS view is displayed.
- Run frr
The IS-IS FRR view is displayed.
- Run loop-free-alternate [ level-1 | level-2 | level-1-2 ]
IS-IS LFA is enabled, and LFA links can be generated.
- Run ti-lfa [ level-1 | level-2 | level-1-2 ]
IS-IS TI-LFA is enabled.
- (Optional) Run tiebreaker { node-protecting | lowest-cost | non-ecmp | srlg-disjoint } preference preference [ level-1 | level-2 | level-1-2 ]
The solution of selecting a backup path for IS-IS TI-LFA FRR is set.
By default, the priority of the node-protection path first solution is 40, the priority of the smallest-cost path first solution is 20, the priority of the non-ECMP first solution is 10, and the priority of the Shared Risk Link Group (SRLG) disjoint first solution is 5. A larger value indicates a higher priority.
Before configuring the srlg-disjoint parameter, you need to run the isis srlg srlg-value command in the IS-IS interface view to configure the IS-IS SRLG function.
- Run quit
Return to the IS-IS FRR view.
- Run quit
Return to the IS-IS view.
- (Optional) After completing the preceding configuration, IS-IS TI-LFA is enabled on all IS-IS interfaces. If you do not want to enable IS-IS TI-LFA on some interfaces, perform the following operations:
- Run commit
The configuration is committed.
- If a network fault occurs or is rectified, an IGP performs route convergence again. A transient forwarding state inconsistency between network nodes results in inconsistent convergence rates on devices, posing a risk of microloops. To prevent microloops, perform the following operations:
Run isis [ process-id ]
An IS-IS process is enabled, and the IS-IS view is displayed.
- Run avoid-microloop frr-protected
IS-IS local microloop avoidance is enabled.
- (Optional) Run avoid-microloop frr-protected rib-update-delay rib-update-delay
The delay in delivering IS-IS routes is set.
Run avoid-microloop segment-routing
The IS-IS remote microloop avoidance function is enabled.
(Optional) Run avoid-microloop segment-routing rib-update-delay rib-update-delay
The delay in delivering IS-IS routes in a segment routing scenario is set.
Run commit
The configuration is committed.