The isis ipv6 bfd incr-cost command configures an interface to adjust its cost based on the status of an associated IPv6 BFD session.
The undo isis ipv6 bfd incr-cost command cancels this configuration.
The isis ipv6 bfd incr-cost block command blocks an interface from adjusting its cost based on the status of an associated IPv6 BFD session.
The undo isis ipv6 bfd incr-cost block command cancels this configuration.
By default, an IS-IS interface does not adjust its cost based on the status of an associated BFD session.
By default, an IS-IS interface is not blocked from adjusting its cost based on the status of an associated IPv6 BFD session.
| Parameter | Description | Value |
|---|---|---|
| cost-value |
Specifies a cost increment value for the interface. |
The value is an integer ranging from 1 to 16777213. |
| max-reachable |
Changes the cost of the interface to the maximum value 16777214. |
- |
| ipv6 |
Indicates the IPv6 protocol. |
- |
| block |
Blocks the IS-IS interface from adjusting its cost based on the status of an associated BFD session. |
- |
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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 IPv6 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 isis ipv6 bfd incr-cost command on an IS-IS interface to configure the interface to adjust its cost based on the status of an associated BFD session. If the interface detects a IPv6 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 IPv6 BFD session is not preferentially selected, and traffic is transmitted through other links. When the interface detects that the IPv6 BFD session goes up, the interface automatically restores its cost to the original value.Prerequisites
IPv6 BFD has been enabled on the interface using the isis ipv6 bfd 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 isis ipv6 bfd incr-cost and isis ipv6 bfd incr-cost block commands are mutually exclusive. If you run both commands, the latest configuration overrides the previous one. The linkcost of an interface depends on the cost type:<HUAWEI> system-view [~HUAWEI] interface Ethernet 0/1/17 [*HUAWEI-Ethernet0/1/19] ipv6 enable [*HUAWEI-Ethernet0/1/19] isis ipv6 enable [*HUAWEI-Ethernet0/1/17] isis ipv6 bfd incr-cost 2