2.9.5 Unavailability of DNS
DNS can be used by clients of the Active Directory system in order to locate directory servers by using the algorithms described in [MS-ADTS] section 6.3. If DNS ceases to be available (for example, by failure of the DNS servers), any clients that use those location algorithms will be unable to find a directory server to send their requests to. This will not affect any connections that clients already have to the directory server. Additionally, clients are permitted to use other means to locate a directory server (for example, by prompting the user to enter the IP address of a directory server) or to store and reuse the address of a previously located directory server. Such clients will also not be immediately affected by the loss of DNS.
After DNS is restored to normal operating behavior, clients that depend on the location algorithms of [MS-ADTS] section 6.3 can once again locate directory servers.