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6.4 Other Windows Resolvers
Since you probably have hosts running other versions of Windows on
your network, it's helpful to know how these
resolvers behave, too.
6.4.1 Windows 95
Windows 95 includes
its own
TCP/IP stack with a DNS
resolver. In fact, Windows 95 actually
includes two TCP/IP stacks: one for TCP/IP over LANs and another for
TCP/IP over dial-up connections. To get to the main DNS configuration
panel, go to the Control Panel, then select Network. Select TCP/IP, then click the Properties button. This brings up a new
dialog, which looks similar to the one in Figure 6-10. Choose the tab labeled DNS Configuration.
Figure 6-10. Resolver configuration under Windows 95
Configuration using this panel is fairly self-explanatory: first
select Enable DNS to turn on DNS
resolution, then fill in the PC's hostname (in this
case, the first label of its domain name) in the Host field and the local domain name
(everything after the first dot) in the Domain field. Add the IP addresses of up to
three name servers you want to query, in the order in which you want
to query them, under DNS Server Search
Order. Finally, fill in the domain names in the search
list under Domain Suffix Search
Order in the order in which you want them appended. If you
leave out the Domain Suffix Search
Order, the Windows 95 resolver derives one from the local
domain name in the same way a Windows 2000 resolver does: appending
successive parent domains with at least two labels.One interesting note about Windows 95: you can configure a different
set of name servers for each dial-up connection you might have to an
ISP in the Dial-Up Networking (DUN) configuration. To configure
DUN-specific resolver settings, double-click on the My Computer icon on your desktop, then
double-click on Dial-Up Networking,
right-click on the name of the connection whose resolver settings
you'd like to configure, and select Properties. Select the Server Types tab and click on TCP/IP Settings. You'll see
the window shown in Figure 6-11.
Figure 6-11. DUN resolver configuration under Windows 95
If you leave the Server assigned name server
addresses radio button checked, the resolver retrieves the
name servers it should query from the server you dial into. If you
check Specify name server addresses
and specify the addresses of one or two name servers, Windows 95
tries to use those name servers when the DUN connection is active.This is really useful if you use multiple ISPs and each has its own
name servers. However, configuring name servers in the TCP/IP Properties panel overrides the
DUN-specific name servers. To use the DUN-specific name server
feature, you must leave the TCP/IP
Properties panel blank except for enabling DNS and
specifying the local hostname. This limitation is due to a lack of
integration between the dial-up and LAN TCP/IP stacks and is
corrected in DUN 1.3. See Knowledge Base article 191494 for details.
6.4.2 Windows 98
The resolver in
Windows 98 is almost identical to
Windows 95's resolver. (Graphically, in fact, it
is identical, so we won't show
you any screenshots.) The major differences between the two resolvers
are due to the fact that Windows 98 ships with Winsock 2.0.[8] Winsock 2.0,
for example, sorts responses as we described in the previous section
on subnet prioritization. For details, see Knowledge Base article
182644.[8] The version of Winsock in Windows 95 can be upgraded to 2.0;
see Knowledge Base article 182108.
Configuring DUN-specific name servers also works with Windows 98. The
resolver queries the name servers listed in the TCP/IP Properties panel and the DUN-specific
name servers simultaneously and takes the first positive answer it
receives from either set. If the resolver receives only negative
answers, it returns a negative answer.
6.4.3 Windows NT 4.0
In
Windows NT,
LAN
resolver configuration is done from a single panel that looks
remarkably similar to Windows 95's, since NT 4.0
incorporated the Windows 95
"shell." In fact, other than the
presence of the new Edit button and
the handy little arrows that allow you to reorder name servers and
elements of the search list, there's really no
semantic difference between them, as shown in Figure 6-12.
Figure 6-12. Resolver configuration under Windows NT
To get to the DNS Configuration
panel, go to the Control
Panel, click on Network, and select the Protocols tab. Double-click on TCP/IP Protocol, then select the DNS tab.Windows NT also allows users to configure resolver settings specific
to particular dial-up networking connections. To configure these,
click on the My Computer icon,
select Dial-Up Networking, pull down
the top selection box, and choose the name of the DUN connection
whose resolver you'd like to configure. Then click
on the More pull-down and select
Edit Entry then Modem Properties. Select the Server tab on the resulting window, and click
on the TCP/IP Settings button.
You'll see the same window you'd
see in Windows 95 (shown earlier).If you leave the Server assigned name server
addresses radio button checked, the resolver retrieves the
name servers it should query from the server you dial into. If you
check Specify name server addresses
and specify the addresses of one or two name servers, Windows NT uses
those name servers when the DUN connection is active. When you drop
the DUN connection, NT reverts to using the LAN
resolver's settings.The Windows NT 4.0 resolver caches name-to-address mappings on a
per-process basis, according to the TTL on the returned address
records, as mentioned earlier.Microsoft updated the resolver fairly extensively in Windows NT 4.0,
Service Pack 4. The SP4 resolver supports subnet prioritization. See
Microsoft Knowledge Base article 196500 for details. The SP4 resolver
also lets you turn off caching in the resolver using a Registry
value. For details, see Knowledge Base article 187709. The SP4
resolver uses the same, more aggressive retransmission algorithm as
the Windows 2000 resolver. See Knowledge Base article 198550 for more
information.
