Notes from the lab — segment routing, automation, and advanced networking
I write about what I'm actually working on — live lab experiments, protocol deep-dives, automation scripts, and lessons learned from things that didn't work the first time. Posts are technical and assume a networking background. Connect on LinkedIn if you want to discuss anything here.
Running a full SR-MPLS topology on Cisco XRd 25.3.1 — IS-IS with SR extensions, Flex-Algo delay-based routing, a live PCE/PCEP session computing paths dynamically, and TI-LFA providing sub-second failover. Includes real command output and a live failure/recovery scenario with timestamps.
Writing NETCONF automation against IOS-XR for a service provider topology — which YANG models expose the data you actually need, how to navigate the model structure, and a working Python collector that pulls IS-IS adjacencies, SR-TE policy state, and BGP prefix counts from every node in the fabric.
The same SR-MPLS concepts work on both platforms but the configuration syntax is surprisingly different. Side-by-side comparison covering SRGB definition, prefix-SID placement, TI-LFA scope, SR-TE policy structure, and BGP color community handling — useful for engineers working in multi-vendor SP environments.
IS-IS is the dominant IGP in service provider networks and the underlay for every SR-MPLS deployment. Covers area design, wide metrics, multi-topology for IPv6, SR extensions, and the operational differences that matter when you're running IS-IS at carrier scale on IOS-XR.
LDP is still the label distribution protocol in the majority of production SP networks despite SR-MPLS gaining ground. Covers LDP sync with IGP, session protection to survive link failures, graceful restart, and unified MPLS for seamless label continuity across domain boundaries — all on IOS-XR with real lab output.
L3VPN is the foundational SP service — understanding PE/P/CE roles, VRF instantiation, route distinguishers, and import/export policy with route targets is essential for CCNP and CCIE SP. Built and verified on a live IOS-XR topology with full packet walk from CE to CE across the MPLS backbone.