A multi-session host can be in various states from the time that it is initialized. As a best practice, check that 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 a Multi-session Host
Status Description
Startup Horizon Agent has started on the 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 The host is in the process of being deactivated while sessions are still running on the host. When the sessions end, the status changes to Disabled.
Disabled Process of deactivating the host is complete.
Validating Occurs after Horizon Connection Server first recognizes the host, typically after Horizon Connection Server is started or restarted, and before the first successful communication with Horizon Agent on the 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 Horizon Connection Server deactivates Horizon Agent. This state ensures that a new desktop or application session cannot be started on the host.
Agent unreachable Horizon Connection Server cannot establish communication with Horizon Agent on a host.
Invalid IP Subnet mask registry setting is configured on the host, and no active network adapters have an IP address within the configured range.
Agent needs reboot Component was upgraded, and the host must be restarted to allow Horizon Agent to operate with the upgraded component.
Domain failure The 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 The host is in an unknown state.
Available The 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.
Drain The host is in drain mode and not accepting new connections.
Drain mode until restart The host is in drain mode and not accepting new connections until it is restarted.