Phased AWS Transit Gateway to AWS Cloud WAN Migration with Terraform and Network MCP Server

This article presents a six-phase migration approach using Terraform and AWS Network MCP Server to transition from AWS Transit Gateway to AWS Cloud WAN while maintaining production workload availability.

• Pre-migration discovery using MCP Servers to inventory existing AWS Transit Gateway topology and validate hybrid connectivity requirements
• Phase 1: Deploy AWS Cloud WAN foundation with Core Network Edges and segments matching existing architecture
• Phase 2: Establish peering between AWS Transit Gateway and AWS Cloud WAN, create policy tables, and attach route tables to segments
• Phase 3: Remove static peering routes to enable cross-Region traffic through AWS Cloud WAN CNEs
• Phase 4: Migrate hybrid connectivity (VPN, SD-WAN, AWS Direct Connect) to AWS Cloud WAN while maintaining AWS Transit Gateway as backup
• Phase 5: Integrate AWS Network Firewall using Network Function Groups for optimized traffic inspection paths
• Phase 6: Migrate production workloads and decommission AWS Transit Gateway after validation
• Use MCP Servers for natural language validation of routes, configuration drift detection, and real-time network state visibility

This structured, phased approach reduces migration risk through incremental validation, automates manual coordination across teams, and provides visibility into complex routing scenarios using reusable Terraform modules.