IS-IS Part 2: Multi-Area Hierarchy, ATT Bit, and Route Leaking
This guide covers the design, provisioning, and verification of Multi-Area IS-IS across the Nokia SR OS topology. We examine Level 1 and Level 2 database partitioning, the Attached (ATT) bit default routing mechanism, route summarization with black-hole loop prevention, and policy-based Level 2 to Level 1 route leaking using the Up/Down bit. SR OS Version: 25.7.R1 CLI Mode: MD-CLI (Model-Driven CLI) [!NOTE] Prerequisites and Physical Foundation: This lab builds directly upon the operational single-area fabric established in IS-IS Part 1: Single-Area Fundamentals, Adjacencies, and LSDB Synchronization. Base interface configuration, card provisioning, port breakouts, and /30 transit links remain in service. ...