Transit-Gateway

Question

Hello,

I created two different VPCs. In the right VPC, I created both a public and a private subnet. In the left VPC, I created only a private subnet. In each private subnet, I created a Linux machine. On the right side, a NAT is defined that allows egress from the private subnet to the public one. In addition, on the right side, an Internet-Gateway is also configured to enable access to the Internet.
In order to connect the two VPCs, I created a Transit-Gateway.
The problem - from the computer in the right VPC I manage to access the Internet (and of course also to the computer in the left VPC). But from the computer in the left VPC, I can only access the computer in the right VPC, but not go online.

Remarks
* I connect to the environments using the AWS-Client-VPN I created.
* I associated the subnets with the respective routing tables.
* I checked all the routings several times.
* I am an AWS associate certified and have extensive knowledge in communication.

I would appreciate your assistance

Accepted Answer

In addition to the other suggestions, make sure that the public subnet on the right has a route to the TGW for traffic going to connected VPCs.

Answer

Is it correct to say that the image is like the following document?  
https://docs.aws.amazon.com/vpc/latest/tgw/transit-gateway-nat-igw.html

Is the subnet where you are setting up the Transit Gateway attachment a private subnet (In the right VPC)?  
Since the route to the NAT Gateway exists on a private subnet, I thought that the subnet where the Transit Gateway attachment is set up must be a private subnet to be able to route it.

Answer

Ensure you have a default route in the left subnet/VPC to route 0.0.0.0/0 to the TGW that’s attached in the private subnet on the right.

In the private the subnet in the right, make sure you have a route back to the subnet on the left.

Transit-Gateway

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