In this repository you will find a CloudFormation Custom Resource which accepts a Transit Gateway Peering Attachment. The Python code for the Lambda can be found in the directory ./transit-gateway-peering-accepter

A Transit Gateway Attachment can be accepted if the state is pendingAcceptance after accepting the attachment it will go into the pending state, if successful the attachment becomes available after 2-5 minutes.

See image below for the whole lifecycle of the attachment:

The Lambda custom resource will wait for the attachment states. The states are handled as follows:

• pendingAcceptance: Accept the peering attachment
• pending, initiating, initiatingRequest: Wait for pendingAcceptance or a failure
• available: Send a SUCCESS response to CloudFormation
• Other states: Throw an exception and send FAILED response to CloudFormation

You can find two CloudFormation examples that implement the custom resource. Two stacks can be found a minimal stack and a full stack.

This is a minimal stack, which only has the Transit Gateway, Peering Attachment and the custom resource peering attachment Accepter.

For deployment of the stack Sceptre is used.

Deploy the minimal stack

sceptre launch transit-gateway-peering-minimal

Destroy the minimal stack

sceptre delete transit-gateway-peering-minimal

This is a full stack, which includes everything from the minimal stack and adds a VPC, EC2 and routes to be able to perform a ping test from both the EC2 instances.

For deployment of the stack Sceptre is used.

Deploy the Full stack

sceptre launch transit-gateway-peering-full

Destroy the Full stack

sceptre delete transit-gateway-peering-full

To get access to the EC2 instances deployed with the 'full' stack you can use SSM. read more about it here