translation method. To conserve public network addresses, Network Address Translation (NAT)
was developed to allow private networks to access the Internet while using a limited amount of
public addressing. In its simplest configuration, NAT operates on a router connecting two
networks. One network, the private intranet, is addressed with either private or obsolete
addresses that need to be converted into public addresses before packets are forwarded onto the
public Internet. A single public address can serve as an alias for multiple sessions between
multiple hosts on the intranet or Internet side of the NAT device. The goal of NAT is to provide
functionality as if the private network had globally unique addresses and the NAT device was
not present.
assigning IP addresses to hosts that are configured to use DHCP. When a DHCP client boots up,
it requests IP addressing information from a DHCP server. When a DHCP server receives the
request, it offers an address from a designated address pool to the DHCP client. The address
can be leased for a specified period of time or leased indefinitely.
addressing changes to be made without impacting the user. A new addressing plan can be
implemented on Friday. When users boot up on Monday, they transparently receive the new
addresses. With DHCP, it is not possible to configure duplicate addresses for hosts.
Troubleshooting the IP network is made simpler because problems that are caused by typos are
eliminated. Figure 5-8 shows a network that is managed by DHCP.