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command. On a Windows NT system, use <strong>the</strong> CLI command shell and type<br />

. On a Windows 95/98 system, from <strong>the</strong> CLI DOS shell or from <strong>the</strong><br />

RUN dialog in <strong>the</strong> Start menu, execute <strong>the</strong> command . On a Macin<strong>to</strong>sh,<br />

<strong>the</strong>re is no native TCP/IP configuration verification method (aside from <strong>the</strong> TCP/IP<br />

Control Panel), so <strong>to</strong> verify TCP/IP operation you need <strong>to</strong> use a third-party <strong>to</strong>ol like<br />

MacTCP Watcher.<br />

NOTE<br />

It is possible <strong>to</strong> use <strong>the</strong> ping command <strong>to</strong> generate a list of <strong>the</strong> reachable hosts on<br />

an IP subnet. The list is generated by pinging <strong>the</strong> broadcast address of <strong>the</strong> IP subnet.<br />

This forces all <strong>the</strong> hosts on <strong>the</strong> subnet <strong>to</strong> reply <strong>to</strong> <strong>the</strong> ICMP request. This option<br />

should be used with caution, especially on CIDR "supernet" address spaces because<br />

it generates <strong>to</strong>ns of <strong>network</strong> traffic. In fact, using <strong>the</strong> ping command in this fashion<br />

can be deadly if used in "fast packet" mode, which sends a burst of messages as fast<br />

as possible at one time, or if a large ICMP message size is configured. For this<br />

reason, filtering out ICMP requests is a wise idea when configuring your router.<br />

In addition <strong>to</strong> performing basic host reachability tests, ping can be used in UNIX and<br />

Windows shell scripts <strong>to</strong> run basic performance checks and perform long-term host<br />

availability moni<strong>to</strong>ring. Here is an example of a performance moni<strong>to</strong>ring <strong>to</strong>ol that<br />

performs a set of pings <strong>to</strong> a host using different ICMP message sizes. Scripts like this<br />

are great for testing for packet loss and measuring transit path performance. This<br />

script runs as a UNIX Cron job and mails <strong>the</strong> test results:<br />

#!/bin/sh<br />

# This script runs as a CRON job sending a group ICMP packets<br />

# of various sizes. The summary results of <strong>the</strong>se transactions are <strong>the</strong>n<br />

# sent via SNMP mail <strong>to</strong> an administra<strong>to</strong>r.<br />

#<br />

# This <strong>to</strong>ol is well suited for measuring WAN and LAN transit link<br />

# performance between file and o<strong>the</strong>r high access/high availability<br />

# devices.<br />

#<br />

# To enable ping fast packet "flooding" add <strong>the</strong> -f flag <strong>to</strong> <strong>the</strong> execution<br />

# command.<br />

#<br />

# Some editing is needed for <strong>the</strong> script <strong>to</strong> operate correctly.<br />

# 1. Define <strong>the</strong> target host.<br />

# 2. Define <strong>the</strong> number of ICMP requests.<br />

# 3. Set <strong>the</strong> UNIX binary paths.<br />

# 4. Set <strong>the</strong> temp direc<strong>to</strong>ry path.

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