isis ipv6 lfa-backup

Function

The isis ipv6 lfa-backup command enables an IS-IS IPv6 interface to participate in Loop-Free Alternate (LFA) calculation.

The undo isis ipv6 lfa-backup command disables an IS-IS IPv6 interface from participating in LFA calculation.

The isis ipv6 lfa-backup disable command disables an IS-IS IPv6 interface from participating in LFA calculation.

The undo isis ipv6 lfa-backup disable command enables an IS-IS IPv6 interface to participate in LFA calculation.

By default, an IS-IS IPv6 interface can participate in LFA calculation.

Format

isis ipv6 lfa-backup [ level-1 | level-1-2 | level-2 ]

undo isis ipv6 lfa-backup [ level-1 | level-1-2 | level-2 ]

Parameters

Parameter	Description	Value
level-1	Enables an IPv6 interface to participate in LFA calculation in a Level-1 area.	-
level-1-2	Enables an IPv6 interface to participate in LFA calculation in Level-1 and Level-2 areas.	-
level-2	Enables an IPv6 interface to participate in LFA calculation in a Level-1 area.	-

Parameter

Description

Value

level-1

Enables an IPv6 interface to participate in LFA calculation in a Level-1 area.

level-1-2

Enables an IPv6 interface to participate in LFA calculation in Level-1 and Level-2 areas.

level-2

Enables an IPv6 interface to participate in LFA calculation in a Level-1 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, 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 IPv6 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 ipv6 lfa-backup command on the IPv6 interface on the link to disable the interface from participating in the LFA calculation.

Prerequisites

IPv6 IS-IS has been enabled running the isis ipv6 enable command on a specified interface.

Precautions

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

Example

# Disable GE 0/1/0 from becoming a backup interface for IPv6 IS-IS auto FRR.

<HUAWEI> system-view
[~HUAWEI] isis 1
[*HUAWEI-isis-1] ipv6 enable
[*HUAWEI-isis-1] quit
[*HUAWEI] interface GigabitEthernet0/1/0
[*HUAWEI-GigabitEthernet0/1/0] ipv6 enable
[*HUAWEI-GigabitEthernet0/1/0] isis ipv6 enable
[*HUAWEI-GigabitEthernet0/1/0] undo isis ipv6 lfa-backup