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Appendix B: Ping and TCP/IP Debugging Tools
Because TCP/IP is so common, Windows
®
and many UNIX
®
systems have built-in tools to help you debug TCP/IP network
problems.
These debugging programs are executed at the command line
prompt of the operating system (see the end of this section for
more information about the command line).
ping
The most popular TCP/IP debugging program is called “ping”
(after the name given to the operation of submarine sonar
devices). Like the sonar, ping sends out a packet to an address
that you specify and waits for a reply. Although very simple to
use, ping is extremely powerful because it works at the IP level
and often will respond even when the higher level TCP layer
cannot. As mentioned above, pinging capability is included
with most systems and there are also many shareware
implementations.
USE: Determine if a workstation is connected to the network.
Routers, servers, and workstations are identified by an IP address
and possibly a “name.” The IP address is a numeric string whose
format is referred to as “dotted decimal” (example:
192.168.0.0.). The “name” can be any name given to a
computer when it is installed or an internet URL. The ability to
use a name is provided by a server’s DNS (Domain Name
Service). The DNS has a lookup table that cross references IP
addresses to names. If a DNS service is not available, you will
need to use the IP address.
EXAMPLE OF USE:
#1: You have problems connecting to the Black Box Web site
from a workstation, and you know the DNS name of the
website is “www.blackbox.com”. At the workstation’s
Command Prompt, enter “ping www.blackbox.com.” If
connected, you will receive back blackbox.com's IP address
(for example, 207.115.64.64) and the roundtrip time of your
ping packet.
