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13.5 Other Command-Line Utilities
The command-line utilities
we've seen so far
cover the spectrum of installing and configuring the DNS Server
service. There are, however, several other utilities that you are
likely to run across as a DNS administrator. They are used for
querying and troubleshooting DNS.
13.5.1 nslookup
The
nslookup utility is one of the oldest and most
widely used DNS tools. With it, you can perform all types of resource
record queries and even zone transfers. This tool is so important
that we spent most of Chapter 12 describing how to
use it.The nslookup utility is installed
by default on Windows 2000, Windows XP, and Windows Server 2003.
13.5.2 ipconfig
The
ipconfig
utility is most commonly used for releasing and renewing DHCP
addresses, but it is also a handy client-side DNS tool. The
DNS-related ipconfig options
include the following:/displaydns
This option displays the contents of the client resolver cache. For
each cached resource record, it displays the Record Name, Record
Type, Time To Live (TTL), Data Length, Section, and RR data. If a
record resides in the cache and another query is made for the record,
the client uses that record (until the TTL expires) instead of
querying a name server again.
/flushdns
This option erases the contents of the resolver cache. Subsequent
lookups are sent to a name server and cached again by the client
after receiving a response.
/registerdns
This option causes the client to refresh its DHCP lease and its
network registration (A and PTR records).
The ipconfig utility is installed
by default on Windows 2000, Windows XP, and Windows Server 2003.
13.5.3 netdiag
The
netdiag utility performs a variety of network
connectivity tests, including a DNS test. The netdiag
/test:DNS command iterates over each active network
adapter and checks whether the hostname has an A record in the domain
specified by the domain suffix for the adapter. If you receive an
error message for the DNS test, you should run
netdiag /test:DNS
/debug, which will produce verbose output and
help pinpoint the cause of the failure.If you run netdiag
/test:DNS on a domain controller and receive
errors, you can run it again with the /fix
option to force all the records in the
netlogon.dns file to be refreshed in DNS. See
Chapter 8 for more details on the
netlogon.dns file.The netdiag utility is available
in the Windows 2000 and Windows Server 2003 Support Tools.
13.5.4 dcdiag
DNS can be hard to configure correctly when initially building an
Active Directory infrastructure. The
dcdiag
utility provides two commands that help assess whether your DNS
infrastructure is configured correctly to support Active Directory.
The /test:DcPromo option can be used to simulate
creating a new forest, domain tree, domain, or replica domain
controller. For this test, you have to include the
/DnsDomain: option and the name of the target
domain. You also need to specify one additional option that indicates
the type of test to run. These include:
/NewForest, /NewTree,
/ChildDomain, and
/ReplicaDC. If you use the
/NewTree option, you must also include the
/ForestRoot: option followed by the name of the
forest root domain. Here is an example command line to test creating
a new child Active Directory domain called
matrix:
C:\> dcdiag test:DcPromo /DnsDomain:matrix.movie.edu /ChildDomain
The other dcdiag test is
RegisterInDNS. It verifies whether a domain
controller can register an A record for its hostname as well as the
various locator records required by Active Directory. The only
additional option that is required for this command is
/DnsDomain: followed by the domain that the
domain controller is in. Here is an example:
C:\> dcdiag test:RegisterInDNS /DnsDomain:movie.edu
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in the Windows 2000 and Windows Server 2003 Support Tools, but the
DcPromo and RegisterInDNS
tests are available only in the latter.
13.5.5 DNSLint
The
DNSLint
utility is new in Windows Server 2003 and provides a way to quickly
check for the existence of one or more resource records on several
name servers. Additionally, it can check for lame delegations, and
the resource records necessary for Active Directory replication to
occur as well as performing connectivity tests for well known email
protocols (i.e., SMTP, POP, and IMAP).The DNSLint utility is part of
the Windows Server 2003 Support Tools. For more information on
DNSLint, see Chapter 15.
13.5.6 dnsdiag
The
dnsdiag
utility can be used to troubleshoot email delivery problems that stem
from DNS misconfigurations. It works by simulating the DNS activity
performed by an SMTP agent that is attempting to deliver email. In
order for dnsdiag to work, either
Exchange or SMTP service needs to be installed on the computer that
dnsdiag is run from. If neither
is installed, you will see a cryptic error stating that
ISATQ.dll was not found.dnsdiag can be found in the
Windows Server 2003 Resource Kit.
