DHCP - Dynamic Host Configuration Protocol

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DHCP (Dynamic Host Configuration Protocol) technology automatically assigns IP addresses to network devices. Many network administrators prefer to use DHCP instead of manually assigning IP addresses.

How DHCP Works

DHCP environments require a DHCP server set up with the appropriate configuration parameters for the given network. DHCP servers assign, then release and renew these addresses as devices leave and re-join the network.

Key DHCP parameters include the range or "pool" of available IP addresses, the correct subnet masks, plus network gateway and name server addresses.

Devices running DHCP client software can then automatically retrieve these settings from DHCP servers as needed. All common network devices including phones, PCs and other consumer gadgets support DHCP, which is built into the software of all common network operating systems.

Using DHCP on Home Networks

Home network equipment like broadband routers offers DHCP support for added convenience in joining home computers to local area networks (LANs)Using DHCP means home network administrators do not need to configure these parameters individually on each client.

Broadband routers provide settings on their console to enable and disable DHCP.  Routers additionally provide several standard configuration options that must be set when DHCP is active.

To manage DHCP for a home network, follow these steps:

  • log into the router as an administrator
  • locate the DHCP settings section inside the router console
  • select the option to turn DHCP on or off
  • if setting DHCP to on, enter the desired private IP address range for local clients. Routers usually prompt for a starting address, a network mask, and a count of the number of addresses that the DHCP server is allowed to assign from its pool.
  • also if setting DCHP on, choose a desired lease time.  In DHCP, a lease represents the length of a time a client is allowed to remain offline from the network until the IP address it was assigned gets returned to the router's DHCP pool, where it can be re-allocated to the same client or other clients.

Using DHCP on the Internet

Internet service providers (ISPs) providers normally use DHCP to allocate public IP addresses to their customers. Because traditional (IPv4) addresses are a scare resource on the Internet, each provider owns only has a limited number and must share them among all active subscribers. DHCP allows providers to reuse a previously-allocated address when that subscriber has remained offline for a set period of time.

Besides the home network's public IP address, Internet providers can allow supply the addresses of their private DNS servers to customers via DHCP.

Limitations of DHCP

Both the client device and the network gateway must support DHCP and have it enabled for automatic address assignment to work.

DHCP servers do not recognize if a device on the network was manually configured with one of the addresses in their pool, a situation that can lead to IP address conflicts.

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