ti-lfa enable

Function

The ti-lfa enable command enables OSPF topology independent-loop free alternate (TI-LFA).

The undo ti-lfa enable command disables OSPF TI-LFA.

By default, OSPF TI-LFA is disabled.

Format

ti-lfa enable

undo ti-lfa enable

Parameters

None

Views

OSPF FRR view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
ospf	write

Usage Guidelines

Usage Scenario

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 a failure to meet reliability requirements.

To satisfy network reliability requirements, TI-LFA is configured to pre-calculate backup links. If a fault occurs, traffic rapidly switches to a backup link before convergence on the control plane is complete. The TI-LFA algorithm is used to calculate the backup links. This algorithm excludes the next hop on the primary LSP or the primary link, re-calculates a shortest path tree (also called a post-convergence tree), and selects a P node and a Q node along the tree. Based on the P and Q node information (see TI-LFA FRR), a label stack for a backup tunnel is generated, directing traffic to be forwarded to the Q node through the tunnel. Upon receipt of a packet, the Q node searches the SR label forwarding table for traffic forwarding based on labels in the packet header.

Prerequisites

Before configuring this command, you need to complete the following configurations:

Global Segment Routing has been enabled using the segment-routing command.
FRR has been enabled and the FRR view has been displayed using the frr command.
OSPF LFA has been enabled using the loop-free-alternate command.

Example

# Enable OSPF TI-LFA.

<HUAWEI> system-view
[~HUAWEI] ospf 1
[*HUAWEI-ospf-1] frr
[*HUAWEI-ospf-1-frr] loop-free-alternate
[*HUAWEI-ospf-1-frr] ti-lfa enable