Configure Network Services - MCSA Windows Server 2012 R2: Installation and Configuration Study Guide - page 152

The DNS server can be updated in two ways. One way is for the DHCP client to tell the
DNS server its address. Another way is for the DHCP server to tell the DNS server when it
registers a new client.
Neither of these updates will take place, however, unless you configure the DNS server
to use Dynamic DNS. You can make this change in two ways:
■ If you change it at the scope level, it will apply only to the scope.
■ If you change it at the server level, it will apply to all scopes and superscopes served by
the server.
Which of these options you choose depends on how widely you want to support
Dynamic DNS; most of the sites I visit have enabled DNS updates at the server level.
To update the settings at either the server or scope level, you need to open the scope or
server properties by right-clicking the appropriate object and choosing Properties. The DNS
tab of the Properties dialog box (see Figure 2.43) includes the following options:
Enable DNS Dynamic Updates According To The Settings Below This check box controls
whether this DHCP server will attempt to register lease information with a DNS server. It
must be checked to enable Dynamic DNS.
Dynamically Update DNS A And PTR Records Only If Requested By The DHCP Cli-
ents This radio button (which is on by default) tells the DHCP server to register the
update only if the DHCP client asks for DNS registration. When this button is active,
DHCP clients that aren't hip to DDNS won't have their DNS records updated. How-
ever, Windows 2000, XP, Vista, Windows 7, Windows 8, Server 2003/2003 R2, Server
2008/2008 R2, and Server 2012/2012 R2 DHCP clients are smart enough to ask for the
updates.
Always Dynamically Update DNS A And PTR Records This radio button forces
the DHCP server to register any client to which it issues a lease. This setting may add
DNS registrations for DHCP-enabled devices that don't really need them, such as print
servers. However, it allows other clients (such as Mac OS, Windows NT, and Linux
machines) to have their DNS information automatically updated.
Discard A And PTR Records When Lease Is Deleted This check box has a long name
but a simple function. When a DHCP lease expires, what should happen to the DNS
registration? Obviously, it would be nice if the DNS record associated with a lease vanished
when the lease expired. When this check box is checked (as it is by default), that's exactly
what happens. If you uncheck this box, your DNS will contain entries for expired leases
that are no longer valid. When a particular IP address is reissued on a new lease, the DNS
will be updated, but in between leases you'll have incorrect data in your DNS—something
that's always best to avoid.
Dynamically Update DNS A And PTR Records For DHCP Clients That Do Not Request
Updates This check box lets you handle these older clients graciously by making the
updates using a separate mechanism.
In Exercise 2.14, you will enable a scope to participate in Dynamic DNS updates.