A Service Principle Name (SPN) is the name by which a client uniquely identifies an instance of a service. By default your IIS machine has SPNs for its hostname, such as myServer, and its Fully Qualified Domain Name (FQDN), such as myServer.branch.example.com.
If the proxy machine is accessed by a name other than either of these, such as myServer.example.com, otherName.company.com, or its IP address, then Active Directory authentication will not work. Your choices are:
HOST/service class for the additional names.
SPNs can be viewed and changed with the
setspn.exe tool, which
Microsoft provides as part of the operating system. More information is