IS-IS IPv6 SRLG TLV 139 and interface-level SRLG configuration

This feature enables routers to advertise and process IPv6 Shared Risk Link Group (SRLG) information as defined in RFC 6119, IPv6 Traffic Engineering in IS-IS, ensuring accurate awareness of shared-risk failures. By extending SRLG support to IPv6 and integrating it directly into the IS-IS configuration, you can deploy SRv6 networks without relying on MPLS. This feature enhances Topology-Independent Loop-Free Alternates (TI-LFA) fast reroute path calculation. It enables faster and more reliable protection against link, node, and shared-risk failures for modern IP networks.

To enable per-interface SRLG configuration and advertisement in IS-IS for SRLG-aware TI-LFA, configure srlg srlg-name at the [edit protocols isis interface interface-name] hierarchy level.