DHCP reduces system admin load
Dynamic Host Configuration Protocol (DHCP) is an Internet Engineering Task Force (IETF) standard for automating the configuration information of computers that use TCP/IP. This protocol reduces system administration workload, allowing devices to be added to the network with little or no manual intervention. DHCP also enable a device to have a different IP address every time it connects to any DHCP enable network. Many ISPs use dynamic IP addressing for dial-up users. Without DHCP, the IP address must be entered manually at each computer and a new IP address must be entered each time a computer moves to a new location on the network.
The DHCP server manages a pool of IP addresses and information about client configuration parameters such as the default gateway, the domain name, the DNS servers, other servers such as time servers, and so on.
When a DHCP-configured client connects to a network, the DHCP client sends a broadcast query requesting necessary information from a DHCP server. Upon receipt of a valid request the DHCP server will assign the computer an IP address, a lease (the amount of time that the DHCP server grants to the DHCP client permission to use a particular IP address), and other IP configuration parameters, such as the subnet mask and the default gateway. The query is typically initiated immediately after booting and must be completed before the client can initiate IP-based communication with other hosts.
Depending on implementation, the DHCP server may have three methods of allocating IP-addresses.
Dynamic allocation: DHCP assigns an IP address from a pool of addresses for a limited period of time chosen by the server, or until the client tells the DHCP server that it no longer needs the address. The request-and-grant process uses the lease concept with a controllable time periods, allowing the DHCP server to reclaim and then reallocate IP addresses that are not renewed.
Automatic allocation: The DHCP server automatically assigns an IP address permanently to a device, selecting it from a pool of available addresses. 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.
Static or manual allocation: The DHCP server allocates an IP address based on a table with MAC address/IP address pairs, which are manually filled in. This will ensure a computer gets the same IP address all the time. Only requesting clients with a MAC address listed in this table will be allocated an IP address.
More than one of the above methods can be used in managing IP address allocation by DHCP servers. For example, a known host on the network can be assigned an IP address based on its MAC address (static allocation) whereas "guest" computers are allocated a temporary IP address out of a pool compatible with the network to which they're attached (dynamic allocation).
By the way, DHCP, like BOOTP runs over UDP, utilizing ports 67 and 68.
The DHCP server manages a pool of IP addresses and information about client configuration parameters such as the default gateway, the domain name, the DNS servers, other servers such as time servers, and so on.
When a DHCP-configured client connects to a network, the DHCP client sends a broadcast query requesting necessary information from a DHCP server. Upon receipt of a valid request the DHCP server will assign the computer an IP address, a lease (the amount of time that the DHCP server grants to the DHCP client permission to use a particular IP address), and other IP configuration parameters, such as the subnet mask and the default gateway. The query is typically initiated immediately after booting and must be completed before the client can initiate IP-based communication with other hosts.
Depending on implementation, the DHCP server may have three methods of allocating IP-addresses.
Dynamic allocation: DHCP assigns an IP address from a pool of addresses for a limited period of time chosen by the server, or until the client tells the DHCP server that it no longer needs the address. The request-and-grant process uses the lease concept with a controllable time periods, allowing the DHCP server to reclaim and then reallocate IP addresses that are not renewed.
Automatic allocation: The DHCP server automatically assigns an IP address permanently to a device, selecting it from a pool of available addresses. 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.
Static or manual allocation: The DHCP server allocates an IP address based on a table with MAC address/IP address pairs, which are manually filled in. This will ensure a computer gets the same IP address all the time. Only requesting clients with a MAC address listed in this table will be allocated an IP address.
More than one of the above methods can be used in managing IP address allocation by DHCP servers. For example, a known host on the network can be assigned an IP address based on its MAC address (static allocation) whereas "guest" computers are allocated a temporary IP address out of a pool compatible with the network to which they're attached (dynamic allocation).
By the way, DHCP, like BOOTP runs over UDP, utilizing ports 67 and 68.
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