Aviatrix TGW Orchestrator FAQ

AWS Transit Gateway Orchestrator simplifies, abstracts, and extends the latest AWS Transit Gateway service. Aviatrix Controller makes Transit Gateway-based Transit architecture deployable by overcoming Transit Gateway limitations.

The AWS Transit Gateway Orchestrator is illustrated in the diagram below.

In the above diagram, AWS VPCs are grouped into four domains: Dev domain, Prod domain, Shared Service domain and Aviatrix Edge domain. Each VPC in the same domain can communicate with each other via AWS Transit Gateway. VPCs in Prod domain cannot communicate with VPCs in Dev Domain, while all VPCs in Dev domain and Prod domain can communicate with Shared service domain and Aviatrix Edge domain.

Through the Aviatrix Transit GW in the Aviatrix Edge domain, Spoke VPCs can communicate with on-prem over Direct Connect.

In the deployment, the VPC in the Aviatrix Edge domain is a Spoke VPC from the Transit Gateway point of view. However, it serves as Transit VPC from the Aviatrix Transit Network point of view. No Aviatrix gateways are deployed in Spoke VPCs except in the Transit VPC.

Aviatrix Transit GW serves as hub connecting to Azure and GCP networks.

The Transit Gateway Orchestrator leverages the Aviatrix Transit Network workflow for the hybrid connectivity function to an on-prem data center and branches. It enables the Transit Gateway Orchestrator to connect with on-prem over Direct Connect or Internet.

The Transit Gateway Orchestrator can also be used as a stand-alone function for orchestrating VPC to VPC connections.

When using the Transit Gateway Orchestrator for hybrid connectivity, no gateways are deployed in the Spoke VPCs for hybrid function.

Transit VPC refers to the transit deployment model where an Aviatrix Gateway is deployed in a Spoke VPC. This is now called "advanced mode" in the AVX Transit.

The Transit Gateway Orchestrator can be deployed with some Spoke VPCs run Aviatrix gateways. When is the right use case to run Aviatrix Spoke gateway?

AWS CloudFormation for Transit Gateway is a resource construct for Transit Gateway. So is the Terraform example.

They are all useful solutions, but these constructs may not be sufficient to run your network.

For example, a Transit Gateway does not propagate routes from on-prem to the VPC route table, meaning there is no guarantee that your VPC instances can reach a specific on-prem server or host. Even if you hard coded the list of CIDRs to shuffle them down to Transit Gateway, what happens when a new VLAN or Subnet is stood up on-prem. Who is going to notify you?

A modern distributed network either requires BGP to dynamically propagate the routes or a controller that dynamically updates the routes. No matter what approach you use, it is the only way to guarantee the network actually functions. At Aviatrix, we choose a software defined approach with our Controller. Unless you plan to develop a Controller like ours, you should consider using our product.

Learn more about Transit Gateway limitations.

The TGW/Transit Segmentation Interoperability feature enables you to extend your AWS TGW network domains into other CSPs. When you are setting up your multicloud transit structure, you can attach an AWS TGW domain to an Aviatrix Transit network domain. Attachments in the AWS TGW network domains can then communicate with Aviatrix Spoke gateways and Site2Cloud connections in the same and in connected Transit network domains.

A Network Domain is an Aviatrix enforced network of VPC members, where VPCs in the Network Domain can communicate with each other, and VPCs not in the Network Domain cannot communicate with VPCs in the Network Domain.

An Aviatrix Network Domain is an abstraction that builds upon the AWS Transit Gateway route table concept. One or more Spoke VPCs are members in a Network Domain.

VPCs in a Network Domain can communicate with each other via a Transit Gateway. Each Network Domain has a corresponding route table on Transit Gateway.

The Aviatrix Controller dynamically programs and updates both VPC route tables so that instances in different Spoke VPCs in the same domain can communicate with each other.

Two Network Domains are not connected, i.e., a Spoke VPC in one domain has no connectivity to another Spoke VPC in a different domain. A connection policy must be specified to connect the two domains so that VPCs in each domain can communicate with each other.

A connection policy is an Aviatrix enforced cross Network Domain connectivity rule.

A connection policy builds upon the Transit Gateway route table propagation concept, it specifies the connection relationship of one Network Domain to others. If there are two Network Domains connected by policy, instances in Spoke VPCs attached to each domain can communicate with each other via Transit Gateway.

In the example below, both Dev_Domain and Prod_Domain have connection policy to Shared_Service_Domain. Dev_Domain and Prod_Domain are not connected. Instances of a VPC in Dev_Domain can communicate with instances of a VPC in Shared_Service_Domain. But instances of a VPC in Dev_Domain cannot communicate with instances of a VPC in Prod_Domain.

Aviatrix Controller programs all VPC route tables and Transit Gateway route tables so that two Network Domains with a connection policy can communicate with each other automatically.

The key use case for building Network Domains is to segment traffic between VPCs, sometimes also called east west traffic.

The benefits are:

Using Network Domains and Connection Policies allow you to identify groups of VPCs with the same requirements from a networking point of view and then apply connection policies at the group level. This avoids having to individually specify connections at the VPC level. The Aviatrix Controller takes care of route programming of all route tables.

One analogy to think of a Network Domain is datacenter VLAN/Subnets and hosts connecting to the VLAN/Subnet.

In the Aviatrix Network Domain concept, a network domain is a VLAN, a host is VPC plugging in to the VLAN. Hosts in the same VLAN can communicate with each other. If two VLANs are defined by policy to be connected, the hosts in different VLAN can communicate with each other.

When a Transit Gateway is created by the Aviatrix Controller, the Default_Domain is created and a route table corresponding to the Default_Domain is created on the Transit Gateway. If you do not plan on building any network segmentation, you can use Default_Domain for inter Spoke VPC and hybrid communications.

When a Transit Gateway is created by the Aviatrix Controller, the Shared_Service_Domain is created and a route table corresponding to the Shared_Service_Domain is created on Transit Gateway.

You can attach a Spoke VPC to this domain and host your shared service instances such as your DevOps tools.

Shared_Service_Domain is always connected to Default_Domain and Aviatrix_Edge_Domain.

When a Transit Gateway is created by the Aviatrix Controller, the Aviatrix_Edge_Domain is created and a route table corresponding to the Aviatrix_Edge_Domain is created on the Transit Gateway.

Aviatrix_Edge_Domain is designated for connecting VPCs managed by the Transit Gateway Orchestrator to on-prem network. There must be one VPC attached to this domain. In the VPC, an Aviatrix Transit GW is deployed and used for data traffic forwarding between Spoke VPCs and on-prem network.

Aviatrix_Edge_Domain is always connected to the Shared_Service Domain and the Default_Domain.

The Transit Gateway Orchestrator is deployed in two stages.

View page provides the following information:

Here are some design patterns that address your requirements.

Yes, all stages (Plan, Build, List, View and Test) are modular. You can change your design any time.

Unlike a VPC, where once you have created it and launched instances in the VPC you cannot delete the VPC or move the instances easily, a Transit Gateway and its attachments can all be changed without making changes to the instances and VPC CIDRs. Simply detach the VPCs from the current Transit Gateway, launch a new Transit Gateway, and build it out again.

The Aviatrix Transit Gateway Orchestrator manages the entire life cycle of the network, including Network Domains, all Transit Gateway and attachments should be created and managed by the Orchestrator.

Since you can create as many network domains as you need, you can create one domain and connect this domain to your Prod domain, and if needed, also to the Dev domain. Simply attach the special VPC to this domain, it will have connectivity to Prod domain.

Transit Gateway significantly simplifies building VPC connections. But the Transit Gateway itself is functionally incomplete for hybrid connection. For example, the Transit Gateway does not propagate routes to Spoke VPCs, which means using a Transit Gateway alone does not offer a functional hybrid solution.

The example below illustrates how CSR based Transit VPC provides an end-to-end solution while a Transit Gateway alone leaves Spoke VPC route table all empty.

The missing function of Transit Gateway is listed as below:

While you may think you can gather the on-prem routes and program the Spoke VPC tables, it is in reality not so simple. The on-prem routes change from time to time as new networks are added or removed, which means you need a reliable way to monitor the route changes, handle exceptions and deal with errors and duplicate routes — essentially a function carried by BGP or an orchestrator.

Aviatrix Transit Gateway Orchestrator fulfills the need to propagate on-prem routes to the Spoke VPCs. This function is either carried by BGP or is software defined. In the Aviatrix case, it is software defined and performed by the Controller. The diagram below shows how the CSR Transit VPC, the Transit Gateway and the Aviatrix Orchestrator compare for route propagation function. As can be seen, in the CSR Transit VPC case, CSR propagates on-prem routes to Spoke VPC via BGP to VGW; the Transit Gateway has no route propagation to Spoke VPC. Aviatrix Controller propagates routes to Spoke VPC through a software-defined mechanism.

An Aviatrix Gateway deployed at the edge/transit VPC provides the following values:

In some cases, you absolutely can. For example, if you have a group of VPCs that need to be connected to each other, you can attach each VPC to the same TGW route table with propagation enabled. Then program each VPC route table with the default route (0.0.0.0/0) to point to TGW.

But in other cases you may not. Using the above example, if there is public subnet in a Spoke VPC, then you cannot simply program each route table with the default route pointing to TGW, as a public subnet already must have its default route pointing to the IGW.

Even a Spoke VPC route table for private subnet may already have the default route point to an AWS NAT gateway. This is quite a common situation and as it happens, you cannot program the default route to the TGW.

However, in the example scenarios above, you maybe able to program RFC 1918 (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) routes of the Spoke VPCs to point to TGW. This is a viable solution you can use to address the issues mentioned above and one that works in a lot of situations.

Yes. The Aviatrix Controller allows you setup a VPN attachment from the Controller directly.

Yes. If you would like to connect your Direct Connect directly into Transit Gateway, the Aviatrix Controller allows you to configure an association between the Direct Connect Gateway and AWS Transit Gateway on the Controller.

AWS Serverless TGW Orchestrator is a solution published by AWS. It orchestrates VPC attachment to a TGW by programming both the TGW route table and VPC route table. The deployment is a Cloudformation Template that contains many AWS services such as Amazon DynamoDB, Amazon EventBridge, Amazon Simple Notification, AWS Lambda function.

Edge Segmentation allows you to further specify on each edge connection which domain it can communicate with.

At Setting up an Aviatrix Transit GW, you can select Edge Segmentation for each connection. When this option is selected, you can then use Build Your Domain Connection Policies to specify which Network Domain this edge connection can communicate with, as shown in the diagram below.

In the above diagram, Site 1 can communicate with Prod domain but not with Dev domain and Shared Service domain. Site 2 can communicate with Dev domain but not with Prod domain and Shared Service domain. Site 3 can communicate with Shared Service domain but not with Dev domain and Prod domain.

Edge Segmentation works across Connection Policies for AWS TGW Peered Network Domains.

To enable Edge Segmentation, go to Multi-Cloud Transit Network > Advanced Config, select the Edit Transit tab, scroll down to AWS TGW Segmentation, and click to set it to Enabled.

Multicast capability function is able to be turned on when users launch AWS TGW. This is API support only.