Product Reviews
A Few of My Favorite Things: NSLookup
Compaq knows a thing or two about troubleshooting large networks. Here are some of the utilities and programs it uses most and likes best for Windows 2000.
Many problems with Internet communications
result from the inability to resolve a domain
name to an IP address. NSLookup is a command-line
utility designed for troubleshooting Domain Name
Service (DNS) problems such as host name resolution.
In Win2K, the utility is installed automatically
with TCP/IP. NSLookup displays all types (“A”
records, CNAME, PTR, MX and so on) and classes
(IN, CS, CH and so on) of DNS resource records.
By default, only Type A records are returned.
The utility can be used either interactively
or non-interactively. To use nslookup interactively,
type “nslookup” at the command prompt. From the
nslookup prompt, type “help” or “?” for a list
of supported commands. Non-interactive mode puts
all commands on one line, preceding subcommands
with a dash.
In interactive mode (see figure), the default server and its address are listed
by the utility. Set the DNS server to one of Compaq’s
public network nameservers to get Compaq’s view
of its public network. Then set the “type” to
“any,” to find all types of records for “compaq.com.”
The returned data shows the domain’s nameservers,
information about the DNS database on the primary
nameserver, MX (mail exchanger) records for compaq.com
and the Internet addresses for the nameservers
and mail exchangers.
 |
| NSLookup can
tell you a lot more than just a server's IP
address. (Click image to view larger version.) |
To see only the MX records for compaq.com,
invoke nslookup with the subcommand preceded by
a dash (-q=MX, setting the query type to MX records),
followed by the DNS name you want to resolve and
the server you want to utilize for that resolution.
One nifty trick to isolate problems
is to use someone else’s DNS server to see if
they can resolve a name your server can’t. To
do this in interactive mode, run through the interactive
session, looking up the domain whose server you’d
like to use. Type:
server
Finally, enter the domain name you
wish to resolve. If the other server can resolve
the name, maybe the problem is with your DNS server.
If not, perhaps the name is wrong or there may
be a problem with that domain’s DNS server.
About the Author
Kendall Wright, MCSE, is a technology
consultant, eGovernment Practice, Compaq Global
Services.