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You can use tracert to ascertain how many hops a particular host is from your workstation. This is useful in determining how fast a link should be. Usually if a host is only a couple of hops away, access should be relatively quick.

The Telnet Utility


TTelnet is an acronym formed from Terminal EmuLation for NETworks and was originally developed to open terminal sessions from remote Unix workstations to Unix server. Although still used for that purpose, it has evolved into a troubleshooting tool. Figure 4.13 shows the basic Telnet interface as it is being used to start a terminal session on a remote Unix host.


FIGURE 4.13 The Windows 95/98 and NT Telnet utility

In today’s Windows 95/98 and NT environments, Telnet is a basic GUI tool for testing TCP connections. You can telnet to any TCP port to see if it is responding, which is especially useful when checking SMTP and HTTP (web) ports. If you’ll remember from Chapter 3, “TCP/IP Fundamentals,” each upper-layer service in a TCP stack has a number for its address. Each network service that uses a particular address will respond to a TCP request


on this port (if the defaults are used). Table 4.6 lists the most commonly referenced port numbers and their associated services.


TABLE 4.6 TCP Port Addresses and Services


Port


TCP/IP Service


21


FTP


23


Telnet


25


SMTP


80


HTTP Session Start


110


POP3 Mail Transfer Protocol


This list is by no means comprehensive. For a complete list, go to

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