isis lfa-backup

Function

The isis lfa-backup command enables an interface to participate in Loop-Free Alternate (LFA) calculation.

The undo isis lfa-backup command disables an interface from participating in LFA calculation.

By default, an IS-IS interface can participate in LFA calculation.

Format

isis lfa-backup [ level-1 | level-1-2 | level-2 ]

undo isis lfa-backup [ level-1 | level-1-2 | level-2 ]

Parameters

Parameter	Description	Value
level-1	Adds an interface to a Level-1 area.	-
level-1-2	Adds an interface to a Level-1 and a Level-2 area.	-
level-2	Adds an interface to a Level-2 area.	-

Parameter

Description

Value

level-1

Adds an interface to a Level-1 area.

level-1-2

Adds an interface to a Level-1 and a Level-2 area.

level-2

Adds an interface to a Level-2 area.

Views

100GE interface view, 10GE interface view, 25GE sub-interface view, 25GE interface view, 400GE interface view, 40GE interface view, 50GE sub-interface view, 50GE interface view, Eth-Trunk interface view, FlexE interface view, GE optical interface view, GE electrical interface view, GMPLS-UNI interface view, Global VE sub-interface view, Loopback interface view, Tunnel interface view, VBDIF interface view, VE sub-interface view, VE interface view, VLANIF interface view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
isis	write

Usage Guidelines

Usage Scenario

By default, FRR calculates a backup link based on the LFA algorithm, and the backup link together with the active link is added to the forwarding table. If an error occurs on the network, FRR can fast switch traffic to the backup link before route convergence on the control plane. This feature ensures uninterrupted traffic forwarding and greatly improves the reliability of IS-IS networks.

By default, an IS-IS interface can participate in LFA calculation. However, some backup links are uncertain when an active link is faulty. To prevent traffic from being transmitted along a link, you can run the undo isis lfa-backup command on the interface on the link to disable the interface from participating in the LFA calculation.

Precautions

To ensure that FRR can function properly, do not disable all interfaces from participating in the LFA calculation.

Example

# Disable GigabitEthernet 0/1/0 from participating in LFA calculation.

<HUAWEI> system-view
[~HUAWEI] isis 1
[*HUAWEI-isis-1] quit
[*HUAWEI] interface GigabitEthernet0/1/0
[*HUAWEI-GigabitEthernet0/1/0] isis enable 1
[*HUAWEI-GigabitEthernet0/1/0] undo isis lfa-backup