1、 计算机网络实验报告年级：计算机科学与技术一班 姓名：刘佳乐 学号：41212022 实验名称：Wireshark Lab:DHCP实验日期：2014.12.11实验目的：了解动态分配地址的过程实验器材：安装 wireshark 的可以联网的电脑实验步骤：开启 Windows 命令提示符，输入：ipconfig /release这个命令释放你当前的 IP 地址，因而主机的IP 地址就变成了 0.0.0.0。1.开启 Ethereal Network Analyzer，开始捕捉数据包；2.现在返回 Windows 命令提示符并输入：Ipconfig /renew这将使你的主机去获取一个网络配置（
2、包括一个新的 IP 地址）。3.等待 ipconfig/renew 执行完毕，然后再次输入：ipconfig /renew4.等第二个 ipconfig/renew 执行完毕后输入命令：ipconfig /release来释放之前你计算机被分配到的 IP 地址；5.最后，再次输入：ipconfig /renew以便再次让你的计算机分配到 IP 地址；7. 停止数据包捕获。回答以下问题：1. Are DHCP messages sent over UDP or TCP?答：UDP2. Draw a timing datagram illustrating the sequence of the
3、first four-packetDiscover/Offer/Request/ACK DHCP exchange between the client and server. For each packet, indicated the source and destination port numbers. Are the port numbers the same as in the example given in this lab assignment?答：与上述实验中给出的 67，68 端口号一致3. What is the link-layer (e.g., Ethernet)
4、address of your host?答：主机链路层的以太网地址是 HonHaiPr_67:65:dd (08:ed:b9:67:65:dd)。4. What values in the DHCP discover message differentiate this message from the DHCP request message?答：根据 DHCP Message Type 的值加以区分。5. What is the value of the Transaction-ID in each of the first four (Discover/Offer/Request/AC
5、K) DHCP messages? What are the values of the Transaction-ID in the second set (Request/ACK) set of DHCP messages? What is the purpose of the Transaction-ID field?答：前四个都是 0x372896fd ，第二组 Request/ACK DHCP 消息中是0xb75f380d，这个字段的目的是为了区分每组 DHCP 的数据。6. A host uses DHCP to obtain an IP address, among other t
6、hings. But a hosts IP address is not confirmed until the end of the four-message exchange! If the IP address is not set until the end of the four-message exchange, then what values are used in the IP datagrams in the four-message exchange? For each of the four DHCP messages (Discover/Offer/Request/A
7、CK DHCP), indicate the source and destination IP addresses that are carried in the encapsulating IP datagram.答：客户机一直以 0.0.0.0 作为自己的原地址，服务器以响应的服务器地址作为自己的原地址。客户机与服务器一直以 255.255.255.255 最为目的地址。7. What is the IP address of your DHCP server?答：我的 DHCP 服务器的 Ip 地址是 10.136.0.1。8. What IP address is the DHCP
8、server offering to your host in the DHCP Offer message? Indicate which DHCP message contains the offered DHCP address.答：提供给主机的 IP 地址是 10.136.98.41。9. In the example screenshot in this assignment, there is no relay agent between the host and the DHCP server. What values in the trace indicate the abse
9、nce of a relay agent? Is there a relay agent in your experiment? If so what is the IP address of the agent?答：中介代理的 IP 地址是 0.0.0.0 10. Explain the purpose of the router and subnet mask lines in the DHCP offer message.答：供 DHCP 用户在最后收到 ACK 后启动 IP 配置时设置掩码和网关。11. In the DHCP trace file noted in footnote
10、2, the DHCP server offers a specific IP address to the client (see also question 8. above). In the clients response to the first server OFFER message, does the client accept this IP address? Where in the clients RESPONSE is the clients requested address?答：10.136.98.4112. Explain the purpose of the l
11、ease time. How long is the lease time in your experiment?答：租用期是 DHCP 得到 IP 的有效使用期，当有效期过后，DHCP 服务器收回该 IP 地址。有利于 IP 地址的充分利用。租用时间从 ACK 包中获得。租赁时间表明在 2 hours 时间段内此 ip 地址不会再分配给其他主机。13. What is the purpose of the DHCP release message? Does the DHCP server issue an acknowledgment of receipt of the clients D
12、HCP request? What would happen if the clients DHCP release message is lost?答：DHCP Release 消息的作用是为了释放租用的 IP 地址；没有收到；服务器会在其租用时间超出后将其 IP 停用。14. Clear the bootp filter from your Wireshark window. Were any ARP packets sent or received during the DHCP packet-exchange period? If so, explain the purpose of those ARP packets答：有，通过广播查询 IP 是否冲突。实验小结：通过本次实验，对 DHCP 加深了了解。但是还是有不太确定的地方，觉得第四题没有回答到点子上。主要可能还是基础知识不够扎实，还得仔细地看看书。
