Traditionally, Redundancy involves two standard licenses: one license will be applied to the Master Gateway, and the other license will be applied to the Backup Gateway. Since two standard licenses are being used, this approach allows users to disable Redundancy, and set both Gateways to independent modes.
Backup-Only licenses are available for purchase. This license forces the Gateway into a Backup mode, and the mode can not be changed while the license is applied. The benefit of this type of license is that they come at a discounted price. For more details, contact your Account Representative.
If using a Backup only license, the Mode property on the Backup Gateway's Redundancy page will look like the image below.
Instead of the dropdown list that normally appears on this property, the license has forced this Gateway into a Backup mode.
If you would like to change the mode of this Gateway, the backup-only license must first be unactivated. Once unactivated, a new license will need to be applied, otherwise the Gateway will operate in 2 hour trial mode.