Segment Routing
Note: To enable and configure Segment Routing (SR) on the NEs, users need to use CLI as there is no NSP ICM intent type that can provision or configure SR on the NEs in the network. Segment Routing is a prerequisite for creating SR-TE LSPs.
Steps
1 |
Log in to the router via CLI. |
2 |
Configure the IGP instance (OSPF, IS-IS, or both) to signal the router capability TLVs (advertisements). “Area” should be used for OSPF and “AS” should be used for IS-IS. Classic: /configure router ospf advertise-router-capability area /configure router isis advertise-router-capability as MD: /configure router ospf advertise-router-capability area /configure router isis advertise-router-capability as /commit |
3 |
Through CLI, define the Segment Routing Global Block (SRGB) to reserve a range of labels to Prefix-SIDs: Note: In the following example, the range used is [20000, 30000]. Classic: /configure router mpls-labels sr-labels start 20000 end 30000 MD: /configure router mpls-labels sr-labels start 20000 end 30000 /commit |
4 |
If not already done, enable traffic engineering using CLI. This is also not configurable through the use of the pre-defined intent types. Note: If RSVP has already been configured on the network, this step can be skipped. Classic: /configure router ospf traffic-engineering /configure router isis traffic-engineering MD: /configure router ospf traffic-engineering /configure router isis traffic-engineering /commit |
5 |
Through CLI, enable Segment Routing in the IGP instance (OSPF, IS-IS, or both). Also define the “start-label” for the “Prefix-SID” range as well as the “index-range”. Here, if the user chooses “global” as the value, the “'start-label” is equal to the lowest label value in the SRGB and max-index is equal to the range size of the SRGB. Classic: /configure router ospf segment-routing prefix-sid-range global /configure router ospf segment-routing no shutdown /configure router isis segment-routing prefix-sid-range global /configure router isis segment-routing no shutdown MD: /configure router ospf segment-routing prefix-sid-range global /configure router ospf segment-routing admin-state enable /configure router isis segment-routing prefix-sid-range global /configure router isis segment-routing admin-state enable /commit |
6 |
A node-SID index or label value is normally assigned to the NE's primary address (such as a “system” or “loopback” address). The address must be in the GRT (Global Routing Table). Use CLI to configure the index or label to the interface in the IGP instance (OSPF, IS-IS, or both). If both IGP instances are to be configured, a different label/index value must be used as the same value cannot be used. Each router must have a unique label/index value. Example: Defined SRGB: [20000, 30000] Classic NE (e.g. 'Calgary NE'): /configure router ospf 0 area 0.0.0.0 interface "system" node-sid label 20000 /configure router isis 0 interface "system" ipv4-node-sid label 20006 MD NE (e.g. 'Seattle NE'): /configure router ospf 0 area 0.0.0.0 interface "system" node-sid label 20005 /configure router isis 0 interface "system" ipv4-node-sid label 20011 /commit Note: The label/index node-SID value assignment must be different and unique. The chosen value must be a value within the SRGB. End of steps |