The Dynamic Host Configuration Protocol provides configuration parameters to Intenet ( hosts ). DHCP consists of two components: a (protocol ) for delivering host-specific configuration parameters from a DHCP server to a host and a mechanism for allocation of network addresses to hosts. DHCP is built on a client-server model, where designated DHCP server hosts allocate network addresses and deliver ( configuration ) parameters to dynamically configured hosts. DHCP supports three mechanisms for IP address allocation. In "automatic allocation", DHCP assigns a (permanent ) IP address to a client. In "dynamic allocation", DHCP assigns an IP address to a client for a limited period of time. In "manual allocation", a client's IP address is assigned by the network ( administrator ), and DHCP is used simply to convey the assitped address to the client.

动态主机配置协议为互联网上的主机提供配置参数。DHCP由两部分组成:传递从DHCP服务器至主机的具体配置参数的协议以及主机网络地址分配机制。DHCP是建立在客户端-服务器模型之上的,由指定的DHCP服务器向动态配置的主机分配网络地址和传递配置参数。DHCP支持三种IP地址分配机制。在“自动分配”机制中,DHCP分配给客户端一个永久地址。在“动态分配”机制中,DHCP分配给客户端一个临时性的IP地址。在“手动配置”机制中,客户端的IP地址是由网络管理员分配,DHCP仅仅起到配送这个指定的地址给客户端的作用。

Traditional network layer packet forwarding relies on the information provided by network layer( routing)protocols, or static routing, to make an independent forwarding decision at each( hop)within the network. The forwarding decision is based solely on the destination(customer )IP address. All packets for the same destination follow the same path across the network if no other equal-cost(paths )exist. Whenever a router has two equal-cost paths toward a destination, the packets toward the destination might take one or both of them, resulting in some degree of load sharing. Enhanced Interior Gateway Routing Protocol (EIGRP) also supports non-equal-cost(Load)sharing although the default behavior of this protocol is equal-cost. You must configure EIGRP variance for non-equal-cost load balancing.

传统的网络层分组转发是根据网络层路由协议或者静态路由提供的信息,在网络中的每一跳都做出一个独立的转发决策。转发决策只是基于目标单播地址而做出的。如果没有相等费用的其他通路存在,朝着同一目标的所有分组都遵循网路中的同样路径。当路由器具有通向同一目标的相等费用的两条通路时,流向目标的分组就可能走两条通路中的任何一条,这就产生了同样程度的负载共享。增强的内部网关路由协议(EIGRP)也支持不等费用的负载共享,虽然这个协议默认的行为是相等费用的负载共享。通过配置,你可以把EIGRP变为不等费用的负载共享方式。


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