Dynamic Host Configuration Protocol (DHCP) is a client/server protocol based on Bootstrap Protocol (BOOTP) that automatically provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway.Every computer in network needs unique IP address, gateway address, subnet mask and DNS address. We can do it manually, or let to DHCP server to do it automatically instead of us. System will take care that we does not have double IP addresses, that unused addresses are reused, that all addresses are from same range, and it will provide many other less known or needed functions.
On DHCP we must create scope – range of addresses from which IP addresses will be used on clients. Every scope must have defined subnet mask, gateway, and DNS address. This four information are main for work of any client on network.
We can create exclusions, for some IP addresses which should be not in use, for example server IP addresses, which must be static. For example, if server have IP address 192.168.0.2, printer 192.168.0.251, and gateway 192.168.0.255, they can be excluded from scope 192.168.0.1-192.168.0.255.
Also, we can create reservations, IP addresses linked with MAC addresses of client, so one particular client can obtain always same IP address. For example, if Server1 has MAC address of 00:A1:FB:12:45:4C and that computer should always get IP address 192.168.0.2 as its IP address, you can map the MAC address of Server1 with the IP address to configure reservation.
Every address is leased for particular amount of time, after which system check for client presence, and then, extend leasing time if client is present, or put IP address back to pool of free for use addresses, if client is not present. This time is adjustable.