Adding VMware Transit Connect to Egress VPC (Part 3)

Gilles Chekroun

Lead VMware Cloud on AWS Solutions Architect

UPDATE 6 NOV 2020: Github terraform code here

Finally, here is Part 3 of this blog "series" around Egress VPC.

Part 1 is here and Part 2 is here

After setting up the  Egress VPC in part 1 and adding a VPN connected SDDC in part 2 I want to connect the SDDC and the Apps VPCs via a VMware Transit Connect a.k.a. VMware managed Transit gateway.

Lab Setup

Creating an SDDC Group

I have described in deep details the way to create SDDC group and attach Customer VPCs in this article. Let's go and do that quickly.
  1. Create an SDDC group and Attach the SDDC. This step will create the vTGW.
  2. Under "VPC Connectivity" tab, configure the Customer AWS  account number so the vTGW resource can be shared.
  3. On Customer AWS console, go to RAM (Resource Access Manager) and look for "Resources shared  with me"
  4. Accept the vTGW resource

Connecting Apps VPCs

We have now accepted the shared vTGW resource and are able to connect Customer Apps VPCs.

1 - On AWS console, go to VPC, Transit Gateways and select "Transit Gateways Attachments"

2 - Create 2 new attachments and connect the 2 Apps VPCs
3 - The new attachments will be in "pending acceptance" state until we accept them from the VMC console. Since this process is asynchronous, it can take a few mins (I have seen 3 to 10 mins) until we will see the acceptance request in the VMC console. Be patient.

4 - After accepting the VPCs in the VMC console, their state will move to "pending", then "available" and "associated"

Checking the vTGW routes learned in the SDDC

Adding CGW Firewall rules for vTGW

The CGW FW rules will allow traffic to and from the vTGW attached VPCs. We have now a new System Group that includes the VPC prefixes. These rules need to be "Applied to" the Direct Connect interface. It's a bit confusing for now but this is where the SDDC attachment as  "VPC" lives. We are looking to rename it to "DX/vTGW" or something similar.

Update the Apps VPCs route table 

From the Apps VPC point of view we have now 2 TGWs attachments (and by the way the AWS limit is 5). We need to select the proper way out of these VPCs to "TGW-Internet" or vTGW


Voila. At this stage all is ready.

  • SSH to the Ubuntu VM
  • Ping EC2 in Apps VPC 100
  • Ping EC2 in Apps VPC 200
  • Traceroute to the EC2s and verify that no NAT gateways are in the path.

Connection to On-prem

In my lab, I don't have Direct connect and the connectivity to on-prem would be something like:

Next Step

As many of you know, I am a fan of Terraform and my next project will be to automate this lab creation with Terraform.
I will update this post with a Github link when that's done.

Thanks for reading.


  1. Very Useful Content , What tool you use to create Diagrams ?

  2. Great content Guilles! In the last diagram when you talk about "Connection to On-prem", I can connect DX Gateway up to 3 TGWs according to AWS Documentation. But this TGWs (VMware or not) can be in the same region? Thank you for your attention.

    1. In my case they should in the same region just because they connect to the same VPCs.
      In general a DXGW is not linked to a region and the 3 associations can come from different regions


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