Why can't I associate a transit gateway to my Direct Connect gateway?

Resolution

To troubleshoot this issue, do the following:

• Confirm that your Direct Connect gateway isn't associated with a virtual private gateway or private virtual interface. A Direct Connect gateway can be associated with either a virtual private gateway or a transit gateway, but not both. If your Direct Connect gateway is associated with a virtual private gateway or a private virtual interface, then create a new Direct Connect gateway.
• Confirm that your Direct Connect gateway and transit gateway don't have the same Autonomous System Number (ASN). If they have the same ASN, then modify the ASN of your transit gateway. Or, create a new Direct Connect gateway with a different ASN. If you connect to multiple transit gateways that are in different Regions, use unique ASNs for each transit gateway.
• Confirm that you have the required AWS Identity and Access Management (IAM) permissions to associate a transit gateway to your Direct Connect gateway. For more information, see Identity and Access Management for Direct Connect.
• You can attach up only up to three transit gateways to a Direct Connect gateway. Make sure that you aren't exceeding this limit. For more information, see AWS Direct Connect quotas.

Related information

Transit gateway associations