Source Packet Routing in Networking (SPRING) or Segment Routing

Support for UHP in IS-IS SR-MPLS (ACX7020, ACX7100, ACX7332, ACX7348, ACX7509,ACX7024, PTX10002-36QDD, PTX10004, PTX10008, PTX10016, and PTX12008) —Use Ultimate Hop Popping (UHP) with IS-IS or OSPF so the egress provider edge (PE) can process its own node SID. ISIS advertises a node SID with the P flag set and E flag unset. In controller-driven segment routing traffic engineering (SR-TE) the controller inserts the egress PE node SID beneath the SR-TE binding SID. If the Binding SID route fails on the penultimate hop, the egress PE might see its own node SID as the top label instead of penultimate hop popping (PHP). With the P flag set, the PE expects UHP and processes its MPLS label. Include the ultimate-hop-popping statement at the [edit protocols isis source-packet-routing] hierarchy level.

[See ultimate-hop-popping.]

Delay normalization for OSPF Flexible Algorithm metrics and advertisements across IGP instances (ACX7020-AC, ACX7020-AC-C, ACX7020-DC, ACX7020-DC-C, ACX7100-32C, ACX7100-48L, ACX7332, ACX7348, ACX7509, ACX7024, ACX7024X, PTX10001-36MR, PTX10002-36QDD, PTX10003, PTX10004, PTX10008, PTX10016, PTX12008)—Use delay normalization to compute and advertise a normalized delay metric for Flexible Algorithm, to improve path-selection consistency across all IGP instances. The device normalizes each received delay, compares each value with the previously saved normalized value, and triggers link-state advertisement (LSA) generation when the values differ.

Delay normalization is disabled by default. To enable and configure delay normalization, use the normalize interval offset statement at the [edit protocols ospf area interface delay-measurement] hierarchy level.

[See delay-measurement (Protocols OSPF) and How to Configure Flexible Algorithms in OSPF for Segment Routing Traffic Engineering.]

Selectively control per-prefix backup paths with OSPF import policy (ACX7020-AC, ACX7020-AC-C, ACX7020-DC, ACX7020-DC-C, ACX7100-32C, ACX7100-48L, ACX7332, ACX7348, ACX7509, ACX7024, ACX7024X, PTX10001-36MR, PTX10002-36QDD, PTX10003, PTX10004, PTX10008, PTX10016, PTX12008)—You can selectively enable backup paths for specific prefixes to optimize redundancy and resource utilization. By default, a configured backup path applies to all prefixes. To exclude specific prefixes or ranges, create an OSPF import policy and configure the no-backup option in the then clause of the policy to suppress backup path installation for matching routes. You can reserve backup protection for critical prefixes while preventing unnecessary backups for others.

[See Understanding Backup Selection Policy for OSPF Protocol.]

Configure flex-algorithm-preference statement at the [edit protocols ospf] hierarchy level to prioritize desired routes and improve traffic engineering across IP and MPLS domains.

Policy-based redistribution of OSPF prefix SIDs across IGP instances (ACX7020-AC, ACX7020-AC-C, ACX7020-DC, ACX7020-DC-C, ACX7100-32C, ACX7100-48L, ACX7332, ACX7348, ACX7509, ACX7024, ACX7024X, PTX10001-36MR, PTX10002-36QDD, PTX10003, PTX10004, PTX10008, PTX10016, PTX12008)—You can redistribute Segment Routing (SR) prefix-SIDs across OSPF IGP instances using route policy without explicitly specifying a prefix-segment index. This feature standardizes SR labels across instances and improves operational efficiency. Configure a policy with the from prefix-segment statement to match routes carrying prefix-segment information. In the then clause, use prefix-segment redistribute to inherit segment information from the matched route. We also support stitching mpls.0 routes to enable interoperability between different IGP instances.

Non-router-ID endpoints as SR-TE destinations (ACX7020-AC, ACX7020-AC-C, ACX7020-DC, ACX7020-DC-C, ACX7024, ACX7024X, ACX7100-32C, ACX7100-48L, ACX7332, ACX7348, ACX7509, PTX10001-36MR, PTX10001-36MR-K, PTX10002-36QDD, PTX10002-60MR, PTX10003, PTX10004, PTX10008, PTX10016, and PTX12008)—Use non-router-ID endpoints as destinations in Segment Routing—Traffic Engineering (SR-TE) policies for Segment Routing for MPLS (SR-MPLS). Traditionally, these policies use router IDs, but you can specify anycast addresses to enhance redundancy and load balancing in SR-MPLS networks. Use IPv4 and IPv6 anycast addresses as IGP-learned destinations with or without Segment Identifier (SID) stack compression. These anycast addresses are not redistributed (R-bit set). Use them as the to address for SR-TE policies with associated compute profiles..

[See Non-Router-ID Endpoints in Segment Routing Traffic Engineering.]