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Lesson 5
Troubleshooting TCP/IP Addressing
2-45
F02pm08
Figure 2-8
The Internet Protocol (TCP/IP) Properties dialog box
Name Resolution Failures
A common cause of TCP/IP communication problems is a failure to successfully
resolve names into IP addresses. TCP/IP network communication is based on IP
addresses. Every message packet generated by a TCP/IP computer contains a
destina-
tion IP address and a source IP address. IP addresses are difficult for
human beings to
use and remember, however. As a result, the TCP/IP developers devised
services like
DNS and the Windows Internet Name Service (WINS), which enable people to use
friendly names for computers instead of IP addresses.
Name resolution is the process by which a computer converts a name into an
IP
address. In the case of DNS names, for example, the computer sends the name
to a
DNS server, which replies with the IP address associated with the name. The
computer
can then initiate communications using the IP address rather than the name.
If a TCP/IP computer fails to communicate with another computer, it might be
because
the name resolution has failed. This means that the two computers are both
function-
ing properly; they just don’t have the IP addresses they need to
communicate. To test
for a name resolution failure, try to communicate with the destination
computer using
its IP address instead of its name. For example, if you are trying to
contact a Web server
using the uniform resource locator (URL) http://www.adatum.com/home.html and
you
cannot connect, try using the server’s IP address instead of its name, as in
the URL
http://10.112.65.34/home.html. If the connection succeeds, the problem lies
in the
name resolution.
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