Editing Dynamic Host Configuration Protocol (section)

=={{Anchor|LEASE}}Overview==
[[Internet Protocol]] (IP) defines how devices communicate within and across local networks on the Internet.  A DHCP server can manage IP settings for devices on its local network, e.g., by assigning IP addresses to those devices automatically and dynamically.<ref>{{Cite web |title=DHCP - Dynamic Host Configuration Protocol |url=https://routeripnet.com/dhcp/ |website=}}</ref>

DHCP operates based on the [[client–server model]]. When a computer or other device connects to a network, the DHCP client software sends a DHCP [[Broadcasting (networking)|broadcast]] query requesting the necessary information. Any DHCP server on the network may service the request. The DHCP server manages a pool of IP addresses and information about client configuration parameters such as [[default gateway]], [[domain name]], the [[name server]]s, and [[time server]]s. On receiving a DHCP request, the DHCP server may respond with specific information for each client, as previously configured by an administrator, or with a specific address and any other information valid for the entire network and for the time period for which the allocation (''lease'') is valid. A DHCP client typically queries this information immediately after [[booting]], and periodically thereafter before the expiration of the information. When a DHCP client refreshes an assignment, it initially requests the same parameter values, but the DHCP server may assign a new address based on the assignment policies set by administrators.

On large networks that consist of multiple links, a single DHCP server may service the entire network when aided by DHCP relay agents located on the interconnecting routers. Such agents relay messages between DHCP clients and DHCP servers located on different subnets.

Depending on implementation, the DHCP server may have three methods of allocating IP addresses:

;Dynamic allocation: A [[network administrator]] reserves a range of IP addresses for DHCP, and each DHCP client on the [[LAN]] is configured to request an IP address from the DHCP [[Server (computing)|server]] during network initialization. The request-and-grant process uses a lease concept with a controllable time period, allowing the DHCP server to reclaim and then reallocate IP addresses that are not renewed.

;Automatic allocation: The DHCP server permanently assigns an IP address to a requesting client from a range defined by an administrator. This is like dynamic allocation, but the DHCP server keeps a table of past IP address assignments, so that it can preferentially assign to a client the same IP address that the client previously had.

;Manual allocation: This method is also variously called ''static DHCP allocation'', ''fixed address allocation'', ''reservation'', and ''MAC/IP address binding''. An administrator maps a unique identifier (a ''client id'' or [[MAC address]]) for each client to an IP address, which is offered to the requesting client. DHCP servers may be configured to fall back to other methods if this fails.

DHCP services are used for [[Internet Protocol version 4]] (IPv4) and [[IPv6]]. The details of the protocol for IPv4 and IPv6 differ sufficiently that they may be considered separate protocols.<ref>{{cite book |title = The DHCP Handbook |year = 2003 |isbn = 978-0-672-32327-0 |first1= Ralph |last1=Droms |first2= Ted |last2=Lemon |publisher = [[SAMS Publishing]] |page = 436 }}</ref> For the IPv6 operation, devices may alternatively use [[stateless address autoconfiguration]]. IPv6 hosts may also use [[link-local addressing]] to achieve operations restricted to the local network link.