September 24, 2021 By Nicholas Woodyard
Brian Krings
3 min read

The Direct Link and Transit Gateway offerings enable you to connect on-premises network locations to IBM Cloud deployments to support hybrid workloads and keep traffic within the IBM Cloud network.

IBM Cloud Direct Link creates direct, private connections between these on-premises networks and IBM Cloud deployments. IBM Cloud Transit Gateway connects the resources deployed in VPC and classic infrastructures across local and global regions. Now, you can integrate both offerings by using Direct Link to connect your on-premises network to IBM Cloud networks and resources through Transit Gateway.

By default, Direct Link creates a private, direct connection between your on-premises network and IBM Cloud deployment. Optionally, you can choose to create one or more network connections (VPC or classic infrastructure) and attach them to the direct link. Now, you have the option to go one step further by binding your direct links to transit gateways using local gateways or one global gateway.  

After the direct link establishes a secure connection to the transit gateway, your on-premises network receives access to all of the transit gateway’s connections and IBM Cloud resources. In addition, all networks connected to the transit gateway have access to the on-premises network. This is advantageous to large enterprises with mission-critical workloads.

In the following example, the direct link connects to a local transit gateway, along with two VPCs and IBM Cloud classic infrastructure. Inversely, all other networks connected to the transit gateway also connect to the on-premises network:

Note: All connections made to a transit gateway must use unique prefixes (subnets for classic infrastructure). If the VPC prefixes (or subnets) overlap between connections, the network routes become ambiguous, and traffic might fail to reach the desired endpoint.  

Getting started

You can select Transit Gateway as the connection type when you order a direct link, or you can add/update connection type after provisioning a direct link. Keep in mind that if you plan to switch connection types,  you must first remove all attached virtual connections from direct link:

Creating a direct link with a transit gateway connection.

Editing a direct link configuration to change connection types.

After the connection is added successfully, the Virtual connection type shows on the direct link’s details page and in the direct link list view, as shown below:

To complete the connection, navigate to the IBM Cloud Transit Gateway console and initiate a direct link connection using the same IBM Cloud account. Similar to the direct link, you can add a network connection when you create a transit gateway or add connections to existing transit gateways:

Creating a transit gateway with a direct link connection.

Adding a direct link connection in the transit gateway console.

Important: A single direct link instance accepts a maximum of 120 on-premises address prefixes when connected to a transit gateway. Consider aggregating prefixes to keep within this limit.

Learn more

Refer to the following IBM Cloud documentation for more information:

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