The isis prefix-sid command configures a prefix segment ID (SID) for the IP address of a loopback interface.
The undo isis prefix-sid command deletes the prefix SID configured for the IP address of a loopback interface.
By default, no prefix SID is configured for the IP address of a loopback interface.
isis prefix-sid { absolute sid-value | index index-value } [ node-disable ] [ flex-algo flex-algo-id ]
isis process-id process-id prefix-sid { absolute sid-value | index index-value } [ node-disable ] [ flex-algo flex-algo-id ]
undo isis prefix-sid { absolute sid-value | index index-value } [ node-disable ] [ flex-algo flex-algo-id ]
undo isis process-id process-id prefix-sid [ { absolute sid-value | index index-value } [ node-disable ] [ flex-algo flex-algo-id ] ]
undo isis prefix-sid
| Parameter | Description | Value |
|---|---|---|
| absolute sid-value |
Specifies an absolute label value, which is effective SID value. |
The value changes dynamically, depending on the actual situation of the equipment. |
| index index-value |
Specifies a relative label value, also called an offset value. A relative label value plus the smallest value in an SRGB is equal to an absolute value. Effective SID value = index-value + Start SRGB value. The relative label value cannot be out of the SRGB configured locally. A relative label value must be unique in an IS-IS process. If index-value is specified, a local node advertises index-value as a prefix SID. If sid-value is specified, a local node advertises the prefix SID equal to sid-value minus the start SRGB value. |
The value is an integer ranging from 0 to 65534. |
| node-disable |
Specifies to disable the N flag. This parameter disables the TI-LFA algorithm from preferentially selecting nodes with the N flag being disabled. |
- |
| flex-algo flex-algo-id |
Specifies the flexible algorithm identifier. |
The value is an integer ranging from 128 to 255. |
| process-id process-id |
Specifies the ID of an IS-IS multi-instance process. |
The value is an integer ranging from 1 to 4294967295. |
Usage Scenario
To enable a device to advertise a prefix SID to network-wide routers, run the isis prefix-sid command to configure the prefix SID for the IP address of a loopback interface. The prefix SID is used to forward packets along a calculated path.
To enable a device to advertise a prefix SID with an specified flexible algorithm to network-wide routers, run the isis prefix-sid command with the flex-algo parameter to configure the prefix SID with the specified flexible algorithm for the IP address of a loopback interface. The prefix SID is used to forward packets along a calculated path.Prerequisites
IS-IS has been enabled on a loopback interface using the isis enable command.
Segment Routing has been enabled for a specific IS-IS topology using the segment-routing mpls command.Precautions
A loopback interface can be assigned an IP address. The prefix SID will not take effect until an IP address with a 32-bit mask is assigned to the loopback interface.
This command takes effect only on the primary IP address of a loopback interface. If the prefix SID value is beyond the SRGB range, the prefix SID will not be advertised.<HUAWEI> system-view [~HUAWEI] segment-routing [*HUAWEI-segment-routing] commit [~HUAWEI-segment-routing] quit [~HUAWEI] isis 1 [*HUAWEI-isis-1] cost-style wide [*HUAWEI-isis-1] segment-routing mpls [*HUAWEI-isis-1] quit [*HUAWEI] interface loopback0 [*HUAWEI-LoopBack0] isis enable 1 [*HUAWEI-LoopBack0] isis prefix-sid index 100 flex-algo 128
<HUAWEI> system-view [~HUAWEI] segment-routing [*HUAWEI-segment-routing] commit [~HUAWEI-segment-routing] quit [~HUAWEI] isis 1 [*HUAWEI-isis-1] cost-style wide [*HUAWEI-isis-1] segment-routing mpls [*HUAWEI-isis-1] quit [*HUAWEI] interface loopback0 [*HUAWEI-LoopBack0] isis enable 1 [*HUAWEI-LoopBack0] isis prefix-sid index 100