Native Transit Gateway Attachment Reshapes AWS Network Firewall Architectures

AWS has detailed the migration architecture for natively attaching AWS Network Firewall directly to AWS Transit Gateway as a managed network function attachment. In traditional centralized inspection deployments, organizations had to provision and maintain a dedicated inspection Amazon VPC containing firewall subnets, elastic network interfaces, and intricate route tables to funnel inter-VPC (east-west) and egress (north-south) traffic through inspection engines. With native attachment, AWS deploys and manages the firewall endpoints within an AWS-managed VPC, allowing network teams to route traffic directly through the Transit Gateway attachment without owning or maintaining the underlying inspection infrastructure. This architectural evolution addresses two persistent operational challenges for cloud networking and FinOps teams: topology complexity and cost allocation. Operating dedicated inspection VPCs requires maintaining secondary route tables, monitoring intermediary subnets, and troubleshooting asymmetric routing during multi-Availability Zone failovers. By converting the firewall into a first-class Transit Gateway attachment, network architects eliminate an entire tier of custom routing and infrastructure management. Crucially, native attachment integrates with Transit Gateway metering policies, enabling organizations to accurately apportion Network Firewall data processing charges back to specific spoke VPCs and account owners—a capability previously hindered when traffic traversed an intermediary inspection VPC. This development reflects a broader cloud networking trend toward collapsing artificial infrastructure boundaries in favor of declarative, managed service attachments. Just as major cloud providers have abstracted overlay appliances into managed gateway endpoints and modern service fabrics, enterprise transit routing is moving away from DIY choke-point VPCs toward native inline security functions. As enterprise cloud footprints expand to hundreds of accounts and thousands of VPCs supporting microservices and distributed data pipelines, monolithic routing topologies become operational bottlenecks. Native service insertion at the transit layer aligns cloud network designs with Zero Trust architectures by decoupling traffic inspection from VPC lifecycle management. For practitioners planning a transition, migration requires deliberate routing choreography. Platform teams should instantiate the Transit Gateway-attached firewall in parallel with existing inspection deployments to validate logging, inspect layer 7 rule behavior, and verify symmetric traffic return before cutting over production workloads. Network engineers should migrate spoke VPCs iteratively by associating individual VPCs with dedicated migrated route tables. Finally, teams must assess specific constraints: Transit Gateway encryption is currently unsupported over native attachments, and egress environments requiring static public IP allowlisting must carefully coordinate the transfer of NAT Gateway Elastic IPs to new dedicated egress VPCs during the cutover window.