bfd all-interfaces incr-cost (IS-IS view)

Function

The bfd all-interfaces incr-cost command configures each interface in an IS-IS process to adjust its cost based on the status of an associated BFD session.

The undo bfd all-interfaces incr-cost command restores the default configuration.

By default, no interface in an IS-IS process adjusts its cost based on the status of an associated BFD session.

Format

bfd all-interfaces incr-cost { cost-value | max-reachable }

undo bfd all-interfaces incr-cost [ cost-value | max-reachable ]

Parameters

Parameter	Description	Value
cost-value	Specifies a cost increment value for all interfaces in the IS-IS process.	The value is an integer ranging from 1 to 16777213.
max-reachable	Changes the cost of each interface in the IS-IS process to the maximum value 16777214.	-

Parameter

Description

Value

cost-value

Specifies a cost increment value for all interfaces in the IS-IS process.

The value is an integer ranging from 1 to 16777213.

max-reachable

Changes the cost of each interface in the IS-IS process to the maximum value 16777214.

Views

IS-IS view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
isis	write

Usage Guidelines

Usage Scenario

Either a link fault or topology change on a network will cause routes to be re-calculated within an area. As such, speeding up the convergence of a routing protocol is critical to improving the network performance.

As link faults are inevitable, rapidly detecting these faults and notifying routing protocols is an effective way to quickly mitigate them. This includes associating BFD with a routing protocol to speed up convergence of the routing protocol once a link fault occurs.

On a network where BFD detects a link fault, even if the fault is rectified quickly, the involved interface is disconnected due to the fact that the associated BFD session is down. As a result, the link is unstable and traffic is lost. To prevent this issue and ensure high network reliability, run the bfd all-interfaces incr-cost command in an IS-IS process to configure each interface in the process to adjust its cost based on the status of an associated BFD session. If an interface in the IS-IS process detects a BFD session down event, the interface automatically increases its cost. If an increment value has been specified using cost-value in the command, the interface cost is raised by the specified value. If the max-reachable parameter has been specified in the command, the interface cost is changed to the maximum cost value. In this manner, the problem link associated with the BFD session is not preferentially selected, and traffic is transmitted through other links. When the interface detects that the BFD session goes up, the interface automatically restores its cost to the original value.

Prerequisites

BFD has been enabled in the IS-IS process using the bfd all-interfaces enable command.

Precautions

Regarding the configuration of adjusting the interface cost based on the status of an associated BFD session, the configuration in the interface view takes precedence over that in the IS-IS view.

The linkcost of an interface depends on the cost type:

If the cost type is narrow, narrow-compatible, or compatible, the cost value ranges from 1 to 63.
If the cost type is wide or wide-compatible, the cost value ranges from 1 to 16777214.

Example

# Configure each interface in an IS-IS process to adjust its cost based on the status of an associated BFD session, with the cost increment set to 5. If a BFD session goes down, the associated interface increases its cost by 5.

<HUAWEI> system-view
[~HUAWEI] isis 100
[*HUAWEI-isis-100] bfd all-interfaces incr-cost 5