Configuring a Cisco router or switch as a DHCP server
Dynamic Host Configuration Protocol (DHCP) is a client/server protocol which allows you to allocate network configuration parameters like IP addresses, subnet masks, DNS servers, default gateways and many more to end devices. This protocol uses the UDP ports 67 and 68 as defined in RFC 2131. Nowadays allmost network devices support DHCP including workstations, printers, IP phones, handheld devices etc. Using dynamic IP address assigment you can minimize errors which can appear on manual configuration and also reduce the administrative overhead. Cisco embedded the DHCP server functionality beginning with IOS Version 12.0(1)T. By default, the Cisco IOS DHCP server and relay agent features are enabled but are not configured.