How KMS Works

KMS activation requires Transmission Control Protocol/Internet Protocol (TCP/IP) connectivity. By default, KMS hosts and clients use DNS to publish and find the KMS. The default settings can be used, which require little to no administrative action, or KMS hosts and clients can be configured manually based on network configuration and security requirements.

KMS Activation Renewal

KMS activations are valid for 180 days. This is called the activation validity interval. To remain activated, KMS clients must renew their activation by connecting to the KMS host at least once every 180 days. By default, KMS client computers attempt to renew their activation every seven days. If KMS activation fails, the client will reattempt every two hours. After a client's activation is renewed, the activation validity interval begins again.

Publication of the KMS

The KMS uses service (SRV) resource records (RRs) in DNS to store and communicate the locations of KMS hosts. KMS hosts use Dynamic DNS (DDNS), if available, to publish the KMS SRV RRs. If DDNS is not available, or the KMS host does not have rights to publish the RRs, the DNS records must be published manually or IT professionals must configure client computers to connect to specific KMS hosts. The Volume Activation Deployment Guide at http://go.microsoft.com/fwlink/?LinkId=150083 describes the steps necessary to publish the KMS in DNS.

Note DNS changes may take time to propagate to all DNS hosts, depending on the complexity and topology of the network.