An RDS host can be in various states from the time that it is initialized. As a best practice, check that RDS hosts are in the state that you expect them to be in before and after you perform tasks or operations on them.

Table 1. Status of an RDS Host
Status Description
Startup Horizon Agent has started on the RDS host, but other required services such as the display protocol are still starting. The agent startup period also allows other processes such as protocol services to start up.
Disable in progress RDS host is in the process of being disabled while sessions are still running on the host. When the sessions end, the status changes to Disabled.
Disabled Process of disabling the RDS host is complete.
Validating Occurs after Connection Server first becomes aware of the RDS host, typically after Connection Server is started or restarted, and before the first successful communication with Horizon Agent on the RDS host. Typically, this state is transient. This state is not the same as the Agent unreachable state, which indicates a communication problem.
Agent disabled Occurs if Connection Server disables Horizon Agent. This state ensures that a new desktop or application session cannot be started on the RDS host.
Agent unreachable Connection Server cannot establish communication with Horizon Agent on an RDS host.
Invalid IP Subnet mask registry setting is configured on the RDS host, and no active network adapters have an IP address within the configured range.
Agent needs reboot component was upgraded, and the RDS host must be restarted to allow Horizon Agent to operate with the upgraded component.
Protocol failure The RDP display protocol is not running correctly. If RDP is not running and PCoIP is running, clients cannot connect using either RDP or PCoIP. However, if RDP is running and PCoIP is not running, clients can connect using RDP.
Domain failure RDS host encountered a problem reaching the domain. The domain server was not accessible, or the domain authentication failed.
Configuration error RDS role is not enabled on the server.
Unknown RDS host is in an unknown state.
Available RDS host is available. If the host is in a farm, and the farm is associated with a published desktop or application pool, it will be used to deliver published desktops or applications to users.