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<td bgcolor="#336666"><font face="Arial" size="2" color="#FFFFFF"><b>1.2</font></b></td>
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<font face="Arial" size="2" color="#FFFFFF">DHCP</font></b></td>
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<td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
1.2.5</font></b></td>
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<font face="Arial" size="2" color="#FFFFFF">Configuring DHCP</font></b></td>
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<font face="Arial" size="2"> Like NAT, a DHCP server requires that the
administrator define a pool of addresses. The </font>
<font face="Courier New" size="2"> <b>ip dhcp pool</b></font><font face="Arial" size="2"> command
defines which addresses will be assigned to hosts.<p>The first command, </font>
<font face="Courier New" size="2"> <b>ip dhcp pool</b></font><font face="Arial" size="2">,
creates a pool with the specified name and puts the router in a
specialized DHCP configuration mode. In this mode, use the </font>
<font face="Courier New" size="2"> <b>network</b></font><font face="Arial" size="2"> statement to define the range of addresses to be
leased. <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> If specific addresses on the network are to be excluded,
return to global configuration mode. </p>
<p>The </font>
<font face="Courier New" size="2"> <b>ip dhcp excluded-address</b></font><font face="Arial" size="2"> command configures the router to exclude
an individual address or range of addresses when assigning addresses
to clients. The </font>
<font face="Courier New" size="2"> <b>ip dhcp excluded-address</b></font><font face="Arial" size="2"> command may be used to
reserve addresses that are statically assigned to key hosts, for
instance, the interface address on the router.
<img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"></p>
<p>Typically, a DHCP server will be configured to assign much more than
an IP address. Other IP configuration values such as the default
gateway can be set from the DHCP configuration mode. Using the
</font>
<font face="Courier New" size="2"> <b>default-router</b></font><font face="Arial" size="2"> command sets the default gateway. The address of the
DNS server, </font>
<font face="Courier New" size="2"> <b>dns-server</b></font><font face="Arial" size="2">, and WINS server, </font>
<font face="Courier New" size="2"> <b>netbios-name-server</b></font><font face="Arial" size="2">, can also
be configured here. The IOS DHCP server can configure clients with
virtually any TCP/IP information.</p>
<p>A list of the key IOS DHCP server commands entered in the DHCP pool
configuration mode are shown in Figure
<img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12">.</p>
<p>The DHCP service is enabled by default on versions of Cisco IOS that
support it. To disable the service, use the </font>
<font face="Courier New" size="2"> <b>no service dhcp</b></font><font face="Arial" size="2"> command.
Use the </font>
<font face="Courier New" size="2"> <b>service dhcp</b></font><font face="Arial" size="2"> global configuration command to re-enable the DHCP server process.</p>
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<b>Web Links</b></font></p>
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<p>Configuring DHCP<p>
<a target="_blank" href="http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800ca75c.html">
http://www.cisco.com/en/US/products/sw/
iosswrel/ps1835/ products_configuration_guide_ chapter09186a00800ca75c.html</a></font></p>
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