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| 2.7 |  | DHCP and Easy IP |
| 2.7.1 |  | DHCP overview |

After designing a scalable IP addressing scheme for the enterprise, the next step is implementation. Routers, servers, and other key nodes usually require special attention from administrators. However, desktop clients are often automatically assigned IP configurations using Dynamic Host Configuration Protocol (DHCP). Because desktop clients typically make up the bulk of network nodes, DHCP is good news for systems administrators. Small offices and home offices can also take advantage of DHCP by using Easy IP, a Cisco IOS feature set that combines DHCP with NAT functions.

DHCP works by configuring servers to give out IP configuration information to clients. Clients lease the information from the server for an administratively defined period. When the lease is up, the host must ask for another address, although the host is typically reassigned the same one. -

Administrators typically prefer to use a Microsoft NT server or a UNIX computer to offer DHCP services because these solutions are highly scalable and relatively easy to manage. Even so, the Cisco IOS offers an optional fully featured DHCP server, which leases configurations for 24 hours by default.

Administrators set up DHCP servers to assign addresses from predefined pools. DHCP servers can also offer other information:

- DNS server addresses
- WINS server addresses
- Domain names

Most DHCP servers also allow the ability to define specifically what client MAC addresses can be serviced and to automatically assign the same number to a particular host each time.

> Note: BootP was originally defined in RFC 951 in 1985. It is the predecessor of DHCP, and it shares some operational characteristics. Both protocols use UDP ports 67 and 68, which are well known as BootP ports because BootP came before DHCP.

| Web Links Knowledge: Understanding DHCP http://www.cisco.com/warp/public/779/ smbiz/service/knowledge/ tcpip/dhcp.htm