Standard Operating Procedure (SOP) for Setting up Transit Gateway in AWS

Step 1: Pre-requisites

1. AWS Account: Ensure you have an AWS account with the necessary permissions to create and manage resources.
2. Networking Requirements: Understand the networking requirements of your organization, including IP addressing schemes, routing policies, and connectivity needs.
3. VPCs and Subnets: Have at least two VPCs with non-overlapping CIDR blocks and subnets created within each VPC.
4. Internet Gateway (IGW): If your VPCs require internet access, make sure they are attached to an Internet Gateway.
5. Route Tables: Review and understand the existing route tables in your VPCs, as the transit gateway will require route table associations.

Step 2: Create a Transit Gateway

1. Navigate to Transit Gateway: Sign in to the AWS Management Console and go to the Amazon VPC service.
2. Create Transit Gateway: Click on “Transit Gateways” in the navigation pane and then click “Create Transit Gateway.”
3. Configure Transit Gateway: Provide a name and description for your transit gateway, select the appropriate AWS region, and create the transit gateway.

Step 3: Attach VPCs to the Transit Gateway

1. Navigate to Transit Gateway Attachments: In the Transit Gateway dashboard, click on “Transit Gateway Attachments.”
2. Create Attachment: Click “Create Transit Gateway Attachment” and select the transit gateway you created earlier.
3. Attach VPCs: Choose the VPCs you want to attach to the transit gateway and specify the subnets within each VPC to be associated with the attachment.

Step 4: Update Route Tables

1. Navigate to Route Tables: In the VPC dashboard, go to “Route Tables.”
2. Update Route Tables: Update the route tables associated with the subnets in your VPCs to route traffic destined for other VPCs or on-premises networks through the transit gateway.

Step 5: Attach VPN Connections or Direct Connect

1. VPN Connections: If you have VPN connections, navigate to the VPN Connections section in the VPC dashboard and attach them to the transit gateway.
2. Direct Connect: If you have AWS Direct Connect, attach it to the transit gateway as well.

Step 6: Test Connectivity

1. Ping Tests: Perform ping tests between instances in different VPCs to ensure connectivity through the transit gateway.
2. Traffic Tests: Test various types of traffic (e.g., HTTP, HTTPS, SSH) to validate connectivity and proper routing.

Step 7: Monitoring and Maintenance

1. CloudWatch: Set up CloudWatch alarms to monitor the health and performance of your transit gateway.
2. Regular Maintenance: Periodically review and update route tables, attachments, and security settings as your network evolves.

By following this SOP, you should be able to successfully set up a transit gateway in AWS, facilitating efficient and scalable connectivity between your VPCs and on-premises networks.