Ensure to define VPC associations and propagations yourself to keep track of all routes and connections to and from your Transit gateway

Risk Level: Low
Cloud Entity: AWS Transit Gateway
CloudGuard Rule ID: D9.TF.AWS.NET.59
Covered by Spectral: No
Category: Networking & Content Delivery

GSL LOGIC

aws_ec2_transit_gateway should have default_route_table_association regexMatch /disable/i and default_route_table_propagation regexMatch /disable/i

REMEDIATION

Perform the following steps in order to set 'Default route table association' and 'Default route table propagation' to disable:
From Portal

1. Sign in to the Amazon VPC console at https://console.aws.amazon.com/vpc/
2. Choose Transit Gateways
3. Choose relevant gateway and click Actions -> Modify.
4. Uncheck 'Default route table association' and 'Default route table propagation'.
5. Update route table with the necessary routes.

From CLI
aws ec2 modify-transit-gateway --transit-gateway-id <Transit gateway ID> --options DefaultRouteTableAssociation=disable,DefaultRouteTablePropagation=disable

From TF

resource "aws_ec2_transit_gateway" "example" {
	- default_route_table_propagation  = "enable"
	+ default_route_table_propagation  = "disable"
}

References
https://docs.aws.amazon.com/vpc/latest/tgw/tgw-getting-started.html
CLI: https://awscli.amazonaws.com/v2/documentation/api/latest/reference/ec2/modify-transit-gateway.html

AWS Transit Gateway

AWS Transit Gateway connects VPCs and on-premises networks through a central hub. This simplifies your network and puts an end to complex peering relationships. It acts as a cloud router ��� each new connection is only mad

Compliance Frameworks

• Terraform AWS CIS Foundations