Dynamic Host Configuration Protocol

in Ip-address

Dynamic Host Configuration Protocol works in a client/server mode. DHCP enables clients on an IP network to obtain or lease an IP address or configuration from a DHCP server. This reduces workload when managing a large network. DHCP protocol is described in the RFC 2131.

Most modern operating system includes DHCP in their primary settings, these includes windows OS, Novell NetWare, Sun Solaris, Linux and Mac OS. The clients' requests for addressing configuration from a DHCP network server, the network server manages the assignment of IP addresses and must be obliged to answer to any IP configuration requests from clients.

However, network routers, switches and servers need to have a static IP addresses, DHCP is not intended for the configuration of these types of hosts. Cisco routers use a Cisco IOS features known as Easy IP. This offers an optional but full-featured DHCP server. Easy IP leases address for 24hrs by default, it is most useful in homes and small offices where users can take the advantages of DHCP and NAT without having an NT or UNIX server

How DHCP works

DHCP works by providing a process for a server to assign IP configuration or address to clients. The assigned configuration from the server is for an administratively defined period then it will be withdrawn, when the address is expired, the client must request for another address, although, in most cases the client is issued with the same address. The DHCP sever uses User Datagram Protocol (UTP) as it's transport protocol to send message to the client on port 68, while the client uses port 67 to send messages to the server.
DHCP severs can offer other information, this include, DNS server addresses, WINS server addresses,
Domain names, and in most servers administrators are allowed to define clients MAC addresses, which the server automatically assigns same IP, address each time.


1. The configuration of DHCP on a default router saves time that could be wasted for the configuration of other user workstations. Other device can be simply plugged into the network at any point, and DHCP will automatically allocate an IP address for that location.
2. Because IP configuration is not done manually, this minimizes error; helps in management and centralized control over configuration information.
3. Another remarkable feature of DHCP is the allocation of IP addresses for a given period of time, called the lease period. If a client device decides to keep an allocated IP address for longer than this period, it must renew the lease before it expires. Clients are free to renew their leases as many times as possible.


IP addresses allocated by DHCP are duplicates, and this can cause serious problems on a network, most DHCP servers' track address conflicts. They do this by attempting to ping each IP address before telling a machine or end device that it is safe to use the address. A lot of DHCP clients send an ARP request to verify if the allocated IP address is not already in use before using it. Nevertheless, some DHCP clients and servers do not check before using an address.

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Chika Nwokeoma has 1 articles online

Read more on how to configure DHCP on a Cisco router and Windows at http://www.orbit-computer-solutions.com/DHCP.php.

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Dynamic Host Configuration Protocol

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This article was published on 2010/03/29