1, the establishment of four phases connection
1.1 Discovery Phase
DHCP client DHCP server to find the stage, the client sends the DHCP_Discover in broadcast mode, only DHCP servers respond
1.2 provides stage
DHCP server offers an IP address phase, the DHCP server receives the request of the client, choose from a pool of ip address ip address has not been assigned to the client, the client sends the leased ip address and other settings DHCP_Offer message
1.3 selection phase
DHCP client IP address selection phase, if more than one DHCP server to a client sent a DHCP_Offer message, the client will accept the first received packet, then the individual will respond to the DHCP server in the form of broadcast DHCP_Request message
1.4 confirmation stage
The DHCP server confirms the ip address of the stage, when the DHCP server receives the client to answer DHCP_Request message, the client sends an ip address provided by her and other settings DHCP_ACK confirmation message
2. Configure DHCP experiment
2.1 experimental content
2.2 Experimental topology
2.3 Experimental addressing
2.4 Experimental Procedure
step1: first experiments addressing configured in accordance with the basic configuration
step2: Based Interface Configuration DHCP Server function
First, open the DHCP function on R1
Configuring dhcp select interface command interfaces on two of R1, dhcp open interface functions specified address pool from the interface
step3: Configuring the DHCP SERVER lease-based interface / DNS server address
Lease using dhcp server lease command on the interface on the DHCP server address pool of IP addresses to the default value 1 day 2 days
Address dhcp server excluded-ip-address portion of the address pool is disabled, it is because some addresses need to be assigned to other services, such as DNS servers and HTTP server, so that you can make an address within the range of not participating in the implementation of dynamic allocation, so as to preserve down
指定DNS服务器，为pc2自动分配ip，自动分配地址的DNS服务器地址为8.8.8.8
step4：配置dhcp 客户端，在pc2中选择dhcp模式，命令行输入ipconfig，可以看到ip地址获取成功为192.168.2.253.由此可以看到配置成功！
