动态主机设定协定 (DHCP) 是一种使网络管理员能够集中管理和自动分配 IP 网络地址的通信协议。在 IP 网络中,每个连接 Internet 的设备都需要分配唯一的 IP 地址。 DHCP 使网络管理员能从中心结点监控和分配 IP 地址。当某台计算机移到网络中的其它位置时,能自动收到新的 IP 地址。
DHCP 使用了租约的概念,或称为计算机 IP 地址的有效期。租用时间是不定的,主要取决于用户在某地联接 Internet 需要多久,这对于教育行业和其它用户频繁改变的环境是很实用的。通过较短的租期, DHCP 能够在一个计算机比可用 IP 地址多的环境中动态地重新配置网络。
DHCP 支持为计算机分配静态地址,如需要永久性 IP 地址的 Web 服务器。
DHCP 和另一个网络 IP 管理协议 BOOTP 类似。目前两种配置管理协议都得到了普遍使用,其中 DHCP 更为先进。 某些操作系统,如 Windows NT/2000, 都带有 DHCP 服务器。 DHCP 或 BOOTP 客户端是装在计算机中的一个程序,这样就可以对其进行配置操作。
DHCP信息 The client sends a request to the DHCP server: either to request more information than the server sent with the original DHCPACK; or to repeat data for a particular application - for example, browsers use DHCP Inform to obtain web proxy settings via WPAD. Such queries do not cause the DHCP server to refresh the IP expiry time in its database.
DHCP释放 The client sends a request to the DHCP server to release the DHCP and the client unconfigures its IP address. As clients usually do not know when users may unplug them from the network, the protocol does not mandate the sending of DHCP Release.
客户配置参数 A DHCP server can provide optional configuration parameters to the client. RFC 2132 describes the available DHCP options defined by Internet Assigned Numbers Authority (IANA) - DHCP and BOOTP PARAMETERS.
Options DHCP Option 60 is an option for specifying the Vendor Class Identifier.[1] Within the DHCP there is default route. Option60 is the Vendor ID. Based on this option, you can make special decisions on the CPE to treat the STB. The biggest benefit with using DHCP option 60 is that you do not need to define a port to be bridge or router. Bridging is based on the MAC address of the option 60 so a switch could be connected to the SE567 and have both PC''s and STB''s on a single interface. Option 60 can be used by DHCP clients to identify the vendor and functionality of a DHCP client. The information is a variable length string of characters or octets which has a meaning specified by the vendor of the DHCP client. One method that a DHCP client can communicate that it is using a certain type of hardware or firmware, is to set a value in its DHCP requests called the Vendor Class Identifier (VCI) (Option 60). This method has a DHCP server differentiate between the two kinds of CMs and process the requests from the two types of modems appropriately. Some types of set-top boxes also set the VCI (Option 60) to inform the DHCP server about the hardware type and functionality of the device. The value that this option is set to gives the DHCP server a hint about any required extra information that this client needs in a DHCP response.