You can create a transit virtual interface to connect to a transit gateway, a public virtual interface to connect to public resources (non-VPC services), or a private virtual interface to connect to a VPC.
To create a virtual interface for accounts within your AWS Organizations, or AWS Organizations that are different from yours, create a hosted virtual interface.
See the following to create a virtual interface:
Before you begin, ensure that you have read the information in Prerequisites for virtual interfaces.
To connect your AWS Direct Connect connection to the transit gateway, you must create a transit interface for your connection. Specify the Direct Connect gateway to which to connect.
The maximum transmission unit (MTU) of a network connection is the size, in bytes, of the largest permissible packet that can be passed over the connection. The MTU of a virtual private interface can be either 1500 or 9001 (jumbo frames). The MTU of a transit virtual interface can be either 1500 or 8500 (jumbo frames). You can specify the MTU when you create the interface or update it after you create it. Setting the MTU of a virtual interface to 8500 (jumbo frames) or 9001 (jumbo frames) can cause an update to the underlying physical connection if it wasn't updated to support jumbo frames. Updating the connection disrupts network connectivity for all virtual interfaces associated with the connection for up to 30 seconds. To check whether a connection or virtual interface supports jumbo frames, select it in the AWS Direct Connect console and find Jumbo Frame Capable on the Summary tab.
If you associate your transit gateway with one or more Direct Connect gateways, the Autonomous System Number (ASN) used by the transit gateway and the Direct Connect gateway must be different. For example, if you use the default ASN 64512 for both the transit gateway and the Direct Connect gateway, the association request fails.