Configuring IS-IS Flex-Algo Functions

The Flex-Algos associated with the local prefix SIDs of a device as well as the FADs on the device all need to be advertised through IS-IS.

Context

Each device can use an IGP to advertise their supported Flex-Algos and the related calculation rules through the FAD Sub-TLV.

These Flex-Algos can be associated with prefix SIDs during prefix SID configuration. The IGP can then advertise the Flex-Algos and prefix SIDs through the Prefix-SID Sub-TLV.

Procedure

Globally enable SR.
1. Run system-view
  The system view is displayed.
2. Run segment-routing
  SR is enabled, and the SR view is displayed.
3. Run commit
  The configuration is committed.
4. Run quit
  Return to the system view.
Enable IS-IS to advertise Flex-Algos.
1. Run system-view
  The system view is displayed.
2. Run isis [ process-id ]
  The IS-IS view is displayed.
3. Run network-entity net-addr
  A network entity title (NET) is configured.
4. Run cost-style { wide | compatible | wide-compatible }
  The IS-IS wide metric attribute is configured.
5. Run traffic-eng [ level-1 | level-2 | level-1-2 ]
  IS-IS TE is enabled.
6. (Optional) Run metric-delay advertisement enable [ level-1 | level-2 | level-1-2 ]
  Delay information advertisement is enabled.
  
  In a scenario where IS-IS Flex-Algos calculate paths based on delay information, you need to run this command to enable link delay advertisement through IS-IS.
7. Run segment-routing mpls
  SR-MPLS is enabled.
8. Run segment-routing global-block begin-value end-value [ ignore-conflict ]
  An SRGB range is specified.
  
  If a message is displayed indicating that one or more labels in the SRGB are in use during this configuration, you can select ignore-conflict to allow configuration delivery. However, the configuration does not take effect until the device is restarted and the corresponding labels are released. In normal cases, using ignore-conflict is not recommended.
9. Run flex-algo flexAlgoIdentifier [ level-1 | level-2 | level-1-2 ]
  IS-IS is enabled to advertise Flex-Algos.
10. Run commit
  The configuration is committed.
11. Run quit
  Return to the system view.
Associate a Flex-Algo with a prefix SID.
1. Run system-view
  The system view is displayed.
2. Run interface loopback loopback-number
  A loopback interface is created, and the loopback interface view is displayed.
3. Run isis enable [ process-id ]
  IS-IS is enabled on the loopback interface.
4. Run ip address ip-address { mask | mask-length }
  An IP address is configured for the loopback interface.
5. Run isis prefix-sid { absolute sid-value | index index-value } [ node-disable ] flex-algo flex-algo-id
  A prefix SID is configured for the IP address of the loopback interface.
  
  The flex-algo flex-algo-id parameter allows you to associate the prefix SID with a specified Flex-Algo, so that IS-IS advertises the associated Flex-Algo when advertising the prefix SID.
6. Run commit
  The configuration is committed.