Virtual address for controller in a controller cluster

A non-transitory machine readable storage medium having stored thereon machine readable instructions to cause a computer processor to:

• assign a plurality of Virtual Internet Protocol (VIP) addresses of a subset of unique VIP addresses for use by an external authentication server (EAS), wherein the number of unique VIP addresses is equal to the number of controllers in the NAS controller cluster;
• and
• assign a priority value to each of the plurality of VIP addresses such that a client connected to the NAS controller cluster will have an active controller to authenticate with the EAS and at least one standby controller to authenticate with the EAS in case the active controller fails,
• wherein a number of the plurality of VIP addresses is based on a number of allowable concurrent transactions for a given EAS from a single Internet Protocol (IP) address.

A system comprising:

• a processing resource and
• a memory resource storing machine readable instructions to cause the processing resource to:
• associate a client device with a first Virtual Internet Protocol (VIP) address for use by a first Network Authentication Server (NAS) controller and an external authentication server (EAS) for device authentication;
• associate the client device with a second Virtual Internet Protocol (VIP) address for use by a second NAS controller and the EAS for device authentication;
• in response to an operating failure of the first NAS controller, automatically associate the client device with the first VIP address for use by the second NAS controller and the EAS for device authentication;
• and
• in response to an operating failure of the second NAS controller, automatically associate the client device with the second VIP address for use by the second NAS controller and the EAS for device authentication,
• wherein automatically associating the client device with the first VIP address includes selecting the first VIP address to use based on a first priority value for the first VIP address and a second priority value for the second VIP address, wherein each of the first and second NAS controllers determines the priority value of each VIP address mapped to itself.