Configuring DNS for Active Directory - MCTS Guide to Microsoft Windows Server 2008 Active Directory Configuration - page 360

Figure 9-4

The Properties dialog box for an A record

9. Click View , Advanced from the menu. The Advanced view option shows additional infor-
mation in DNS Manager, such as a new folder called Cached Lookups.
10. Click to expand Cached Lookups and click to expand the .(root) folder. Under the .(root)
folder are one or more subfolders named for TLDs (com, edu, net, and so on). Click to
expand the com folder. Domains you have visited with Vista or Windows Server 2008 have
a folder containing A, NS, and other resource records. Cached entries don't require queries
to external DNS servers.
11. Browse through the folders until you find an A or a CNAME record. (If you can't find one,
start your Web browser and go to www.microsoft.com to create a record in the microsoft
folder. Close your browser and refresh DNS Manager.) Double-click the A or CNAME
record. In the Properties dialog box, you see a time to live (TTL) value, which tells DNS how
long to keep the cached entry. The referring DNS server (an authoritative DNS server for the
domain the record came from) sends the TTL value. Click Cancel .
12. Click the com folder. You should see several NS entries with names in the Data column, such
as a.gtld-servers.net, b.gtld-servers.net, and so on, referred to as “generic top-level domain
(GTLD) servers.” These servers are responsible for com domains throughout the Internet.
Double-click a.gtld-servers.net . Notice that no IP address is associated with the entry. When
your DNS server needs to find the address of a com name server, it must query to find the
address of a TLD server first. Click Cancel .
13. Right-click Cached Lookups and click Clear Cache to delete the cache. There are no entries
in the cache now, except some folders and an entry for localhost. Clear your local DNS cache
by opening a command prompt window, typing ipconfig /flushdns , and pressing Enter .
Close the command prompt window.
14. Start your Web browser, go to any com domain, and then exit your Web browser.
15. Refresh DNS Manager (click Action , Refresh ). Click to expand the .(root) folder, and then
click the com folder. You should see the list of GTLD servers and a folder for the domain
you visited (possibly more than one folder). Click the net folder, and then double-click the
GTLD-SERVERS folder. You see several A records for the GTLD servers listed and perhaps
some AAAA entries with IPV6 addresses.