Add course README with module table of contents and build order

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

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+# ISP Backbone Lab — A Senior Network Engineer's Course
+
+> **Instructor**: Garvis (your friendly neighborhood Sr. Network Engineer)
+> **Platform**: Cisco Modeling Labs (CML) — 32GB RAM budget
+> **Student**: Jordan
+> **Goal**: Build and understand a realistic ISP backbone from the ground up, then attack it.
+
+---
+
+## Table of Contents — Modules
+
+| # | Module | Topic |
+|---|--------|-------|
+| 1 | [Module 1: The Underlay — IS-IS](modules/01-isis.md) | Why every ISP uses IS-IS, Level 2-only design, NET addressing |
+| 2 | [Module 2: MPLS — Labeling the Backbone](modules/02-mpls.md) | Label switching, LDP, Penultimate Hop Popping |
+| 3 | [Module 3: iBGP — The Brain of the ISP](modules/03-ibgp.md) | Route Reflectors, full-mesh problem, loopback peering |
+| 4 | [Module 4: L3VPN — Customer Isolation](modules/04-l3vpn.md) | VRFs, RD vs RT, customer isolation across the MPLS core |
+| 5 | [Module 5: eBGP — Peering with the World](modules/05-ebgp.md) | IXP peering, BGP best path selection (The Big 9), route filtering |
+| 6 | [Module 6: Segment Routing](modules/06-segment-routing.md) | LDP to SR migration, Prefix SIDs, why SR is the future |
+| 7 | [Module 7: Traffic Engineering](modules/07-traffic-engineering.md) | SR-TE policies, SID stacks, Flex-Algo |
+| 8 | [Module 8: Attack & Defense Labs](modules/08-attack-defense.md) | BGP hijacking, IS-IS poisoning, MPLS label manipulation, CoPP |
+
+---
+
+## The Topology
+
+A **two-AS ISP backbone** (AS 65000 and AS 65100) with customer sites, a peering exchange, and an attacker segment.
+
+See the [topology diagrams](diagrams/) for visual references.
+
+## Build Order
+
+### Phase 1: Foundation (Weekend 1)
+- Module 1: IS-IS on all P and PE routers
+- Verify: All loopbacks reachable
+
+### Phase 2: MPLS Core (Weekend 2)
+- Module 2: MPLS/LDP on all core links
+- Module 3: iBGP with Route Reflector
+
+### Phase 3: Services (Weekend 3)
+- Module 4: VRFs and L3VPN
+- Module 5: eBGP peering at the IXP
+
+### Phase 4: Modern SP (Weekend 4)
+- Module 6: Migrate LDP to Segment Routing
+- Module 7: SR-TE policies
+
+### Phase 5: Break Things (Weekend 5+)
+- Module 8: Attack and defense scenarios
+
+## Quick Reference Commands
+
+| What You Want | Command |
+|--------------|---------|
+| IS-IS neighbors | `show isis neighbors` |
+| MPLS labels | `show mpls forwarding-table` |
+| BGP summary | `show bgp summary` |
+| VRF routes | `show ip route vrf CUST_A` |
+| SR SIDs | `show isis segment-routing prefix-sid-map` |