AutoGineer summary
Written by AutoGineer from the skill’s own files, not by the author
This skill provides a structured framework for deploying and managing AWS Transit Gateway, acting as a regional network hub. It streamlines the connection of multiple VPCs and on-premises networks, replacing complex point-to-point peering meshes with a centralized routing architecture. The skill covers the full lifecycle of transit gateway operations, including hub creation, traffic segmentation, centralized egress and inspection, hybrid connectivity, and inter-region peering.
What it does
- Creates and configures regional transit gateway hubs and VPC attachments.
- Implements traffic segmentation using custom route tables to isolate or share network environments.
- Centralizes egress and inspection traffic through dedicated VPCs using appliances or Gateway Load Balancer endpoints.
- Facilitates hybrid connectivity via Site-to-Site VPN and Direct Connect, including ECMP for bandwidth aggregation.
- Manages inter-region peering and migration from existing VPC peering meshes.
- Configures IP multicast routing across attached VPCs.
When to use it
- When you need to connect a large number of VPCs through a single, manageable router.
- When you require centralized inspection of traffic between VPCs or to the internet.
- When you need to isolate network environments while maintaining controlled access to shared services.
- When you are migrating from a complex, unmanageable VPC peering mesh.
- When you need to connect on-premises data centers to multiple VPCs efficiently.
Advantages
- Reduces network complexity by replacing point-to-point connections with a hub-and-spoke model.
- Enables consistent security enforcement through centralized inspection points.
- Supports scalable hybrid connectivity with options for performance optimization.
- Provides granular control over traffic flow via route table associations and propagations.
- Simplifies management of multi-region and multi-VPC network architectures.
Usage examples
- “How do I set up a transit gateway to connect three VPCs and ensure they are isolated from each other?”
- The agent will guide you through creating the transit gateway, attaching the VPCs, and configuring separate route tables to prevent cross-VPC communication.
- “I need to route all outbound traffic from my spoke VPCs through a central inspection VPC using a Gateway Load Balancer.”
- The agent will provide the steps to configure the central inspection VPC, set up the GWLB endpoint, and update route tables to force traffic through the inspection path.
- “Can you help me enable ECMP for my multiple VPN tunnels to increase bandwidth?”
- The agent will verify that you are using dynamic BGP routing and guide you through the configuration to aggregate bandwidth across your VPN tunnels.
- “We are moving off a VPC peering mesh. How do we migrate to a transit gateway without downtime?”
- The agent will outline a migration strategy, including creating the transit gateway, establishing attachments, and incrementally updating routes to transition traffic.
Install
Download the skill as a ZIP:
https://mp-staging.autogineer.com/agent-skills/aws/transitgateway/downloadUnzip it into the cross-client skills folder of your project:
mkdir -p .agents/skills && unzip transitgateway.zip -d .agents/skills
Documentation by AWS
AWS Transit Gateway
Overview
Domain expertise for configuring AWS Transit Gateway, the Regional network hub that connects many VPCs and on-premises networks through a single router instead of a mesh of point-to-point connections. Covers building the hub and attaching VPCs, segmenting traffic with route tables, centralizing egress and inspection, east-west inspection with AWS Network Firewall, hybrid connectivity over Site-to-Site VPN and Direct Connect, inter-Region peering, migrating off a VPC peering mesh, and IP multicast.
This skill is a router. Each customer task maps to a procedure file under references/. Read the
matching reference in full before acting, then follow its constraints and steps. The reference
files are self-contained: each carries its own decision tables, constraints, procedure, and
troubleshooting.
Execute commands using the AWS MCP server when connected (sandboxed execution, audit logging,
observability). Fall back to the AWS CLI otherwise. All CLI operations require least-privilege,
ephemeral credentials (an assumed IAM role through AWS STS or AWS IAM Identity Center / SSO), never
long-lived IAM user access keys. A transit gateway is a Regional resource: run each aws ec2
transit gateway command in the Region that holds the hub.
Which Transit Gateway task do you need?
| Goal | Reference |
|---|---|
| Create a Regional hub and connect VPCs to it | creating a transit gateway and attaching VPCs |
| Isolate some VPCs while letting others share services | segmenting traffic with route tables |
| Send all spoke traffic out through one inspected egress VPC | centralizing egress and inspection |
| Inspect traffic between VPCs with AWS Network Firewall | inspecting east-west traffic with Network Firewall |
| Reach on-premises networks over Site-to-Site VPN or Direct Connect | connecting on-premises networks |
| Link transit gateways in two Regions over the AWS network | peering transit gateways across Regions |
| Move off a VPC peering mesh without dropping traffic | migrating from VPC peering |
| Distribute IP multicast across attached VPCs | routing multicast traffic |
Routing notes
Decide segmentation before you build. "Default route table association" and "Default route table propagation" are on by default, which wires every attachment into one open mesh. If the customer plans isolated environments, the creating reference disables the defaults up front and hands off to the segmenting reference. Retrofitting isolation onto an open hub is a re-architect.
North-south egress vs east-west inspection. Centralizing egress sends spoke traffic out to the internet through a central VPC. East-west inspection keeps traffic between spokes internal and forces it through a firewall on the way. They look similar but use different route table recipes. Match the reference to the direction of traffic the customer actually has.
Appliance vs Gateway Load Balancer for inspection. Raw third-party appliances and a Gateway Load Balancer (GWLB) endpoint are two paths to the same goal. GWLB is the recommended approach for new designs. Both live in the centralizing-egress reference; appliance mode and the GWLB endpoint route table entries differ and the reference covers each.
Appliance mode is required for stateful cross-Availability-Zone inspection, with a tradeoff. Appliance mode keeps each flow on one Availability Zone's appliance so request and response do not split. It also disables cross-Availability-Zone failover for that attachment, so the inspection design must pair it with health-check-based failover. Both the egress and east-west references carry this.
Transit gateway side vs Direct Connect side. The connecting-on-premises reference covers the transit gateway side: Site-to-Site VPN attachment options, route propagation, and equal-cost multi-path (ECMP). The Direct Connect gateway and virtual interface setup belongs to the separate
directconnectskill. Do not restate the Direct Connect side here.
Security considerations
A transit gateway is the central routing point for many VPCs and on-premises networks, so a misconfiguration here has blast radius across every attached network. Apply these controls regardless of the specific task; each per-task reference carries the detail.
You MUST enable Transit Gateway Flow Logs for traffic visibility, audit, and incident response across the hub, and MUST enable encryption at rest on the destination (a KMS key on the CloudWatch log group, or SSE-KMS on the S3 bucket).
You MUST, when a KMS key encrypts a flow log destination (CloudWatch log group or S3 bucket) or a CloudTrail destination, scope the KMS key policy with condition keys (
aws:SourceArn,aws:SourceAccount, andkms:ViaService) so only the specific log group, bucket, or trail in the expected account and service can use the key, preventing cross-account or cross-service misuse.You SHOULD apply least-privilege IAM for transit gateway administration, avoiding service wildcards and FullAccess policies, restricting who can create attachments, modify route tables, and change associations or propagations.
You SHOULD ensure Site-to-Site VPN tunnels use strong encryption (for example AES-256-GCM with IKEv2) and enable tunnel logging to CloudWatch Logs with encryption enabled (a KMS key) to protect sensitive connection state and IKE negotiation detail from unauthorized access (see the connecting on-premises networks reference).
You MUST treat a misconfigured transit gateway route table as a security risk, since wrong associations or propagations can expose workloads across environments meant to stay isolated (see the segmenting traffic reference).
You MUST enable AWS CloudTrail to detect unauthorized changes to transit gateway route tables, associations, and propagations, MUST enable encryption at rest on the CloudTrail destination (a KMS key), and use AWS Config rules to detect drift from the intended design.
Additional Resources
Files
- ATTRIBUTION.mdAdded by AutoGineer939 B
- LICENSELicence file added by AutoGineer9.9 KiB
- NOTICELicence file added by AutoGineer67 B
- SKILL.md7.6 KiB
- references/centralizing-egress-and-inspection.md17.6 KiB
- references/connecting-on-premises-networks.md16.0 KiB
- references/creating-a-transit-gateway-and-attaching-vpcs.md14.1 KiB
- references/inspecting-east-west-traffic-with-network-firewall.md20.4 KiB
- references/migrating-from-vpc-peering.md11.7 KiB
- references/peering-transit-gateways-across-regions.md15.0 KiB
- references/routing-multicast-traffic.md11.8 KiB
- references/segmenting-traffic-with-route-tables.md12.7 KiB
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Requirements and compatibility
Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta
“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.
Needs: Needs an MCP server
Security
No issues found by our static scan· No issues found
A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.
Attribution and licence
- Published by
- AWS
- Publisher
- AWS (Official)
- Source
- aws/agent-toolkit-for-aws · skills/specialized-skills/networking-and-content-delivery-skills/transitgateway · commit 0a218f8
- Licence
- Apache License 2.0 (redistribution allowed)
- LICENSE (added by AutoGineer from LICENSE)
- NOTICE (added by AutoGineer from NOTICE)
- ATTRIBUTION.md (written by AutoGineer)
- Synced
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Download ZIP
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