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<td width="100%" bgcolor="#336666"><b><font face="Arial" size="2" color="#FFFFFF">Overview</font></b></td>
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The rapid growth of the Internet has astonished most observers.
One reason that the Internet has grown so quickly is due to the
flexibility of the original design. Without developing new
methodologies of IP address assignment, this rapid growth of the
Internet would have exhausted the current supply of IP addresses. In order to cope with a shortage of IP
addresses, several solutions were developed. One widely
implemented solution is Network Address Translation (NAT).<p>NAT is a mechanism for conserving registered IP addresses in large
networks and simplifying IP addressing management tasks. As a
packet is routed through a network device, usually a firewall or
border router, the source IP address is translated from a private
internal network address to a routable public IP address. This allows the packet to be transported over
public external networks, such as the Internet. The public address
in the reply is then translated back to the private internal
address for delivery within the internal network. A variation of
NAT, called Port Address Translation (PAT), allows many internal
private addresses to be translated using a single external public
address.</p>
<p>Routers, servers, and other key devices on the network usually require a static
IP configuration, which is entered manually. However, desktop
clients do not require a specific address but rather any one in a
range of addresses. This range is typically within an IP subnet. A
workstation within a specific subnet can be assigned any address
within a range while other values are static, including the subnet
mask, default gateway, and DNS server.</p>
<p>The Dynamic Host Configuration Protocol (DHCP) was designed to
assign IP addresses and other important network configuration
information dynamically. Because desktop clients typically make up
the bulk of network nodes, DHCP is an extremely useful timesaving
tool for network administrators.</p>
<p>Students completing this module should be able to:</p>
<ul>
<li>Identify private IP addresses as described in RFC 1918</li>
<li>Discuss characteristics of NAT and PAT</li>
<li>Explain the benefits of NAT</li>
<li>Explain how to configure NAT and PAT, including static
translation, dynamic translation, and overloading</li>
<li>Identify the commands used to verify NAT and PAT configuration</li>
<li>List the steps used to troubleshoot NAT and PAT configuration</li>
<li>Discuss the advantages and disadvantages of NAT</li>
<li>Describe the characteristics of DHCP</li>
<li>Explain the differences between BOOTP and DHCP</li>
<li>Explain the DHCP client configuration process</li>
<li>Configure a DHCP server</li>
<li>Verify DHCP operation</li>
<li>Troubleshoot a DHCP configuration</li>
<li>Explain DHCP relay requests</font></li>
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