ibm-information-center/dist/eclipse/plugins/i5OS.ic.rzamv_5.4.0.1/rzamvtcpstopdhcp.htm

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<h1 class="topictitle1">Prevent DHCP access</h1>
<div><p>This article discusses the steps for preventing users from accessing
the DHCP server.</p>
<div class="section">If you do not want anyone to use the DHCP server on your system,
do the following:</div>
<ol><li class="stepexpand"><span>To prevent DHCP server jobs from starting automatically when you
start TCP/IP, type the following: <kbd class="userinput">CHGDHCPA AUTOSTART(*NO)</kbd></span> <div class="note"><span class="notetitle">Note:</span> AUTOSTART(*NO) is the default value.</div>
</li>
<li class="stepexpand"><span>To prevent someone from associating a user application, such as
a socket application, with the port that the system normally uses for DHCP,
do the following:</span><ol type="a"><li class="substepexpand"><span>Type <kbd class="userinput">GO CFGTCP</kbd> to display the <span class="uicontrol">Configure
TCP/IP</span> menu.</span></li>
<li class="substepexpand"><span>Select option <span class="uicontrol">4</span> (Work with TCP/IP port
restrictions).</span></li>
<li class="substepexpand"><span>On the Work with TCP/IP Port Restrictions display, specify option <span class="uicontrol">1</span> (Add).</span></li>
<li class="substepexpand"><span>For the lower port range, specify <kbd class="userinput">67</kbd>.</span></li>
<li class="substepexpand"><span>For the upper port range, specify <kbd class="userinput">68</kbd>.</span> <div class="note"><span class="notetitle">Note:</span> The port restriction takes effect the next time that you start
TCP/IP. If TCP/IP is active when you set the port restrictions, you should
end TCP/IP and start it again.</div>
</li>
<li class="substepexpand"><span>For the protocol, specify <kbd class="userinput">*UDP</kbd>.</span></li>
<li class="substepexpand"><span>For the user profile field, specify a user profile name that
is protected on your system. (A protected user profile is a user profile that
does not own programs that adopt authority and does not have a password that
is known by other users.) By restricting the port to a specific user, you
automatically exclude all other users.</span></li>
</ol>
</li>
</ol>
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<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzamvtcpdhcp.htm" title="These topics discuss methods for securing the DHCP server for authorized users and preventing access to the DHCP server.">Security considerations for using DHCP server</a></div>
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