Question

计算机三级网络技术

3.某客户机使用DHCP获取IP地址等信息，其获取IP地址过程中捕获的4条报文及对第2条报文分析如下所示。请分析其中的信息，补全内容。
编号 报文摘要
1 DHCP:Request, Type:DHCP discover
2 DHCP:Reply, Type:DHCP 【11】
3 DHCP:Request, Type:DHCP Request
4 DHCP:Reply, Type:DHCP ACK
DLC: ----- DLC Header -----
DLC: Destination = 【12】
DLC: Source = 001122334455
DLC: Ethertype = 0800 (IP)
IP: D = 【13】 ,S = 192.168.0.1
【14】 : D= 68,S = 67
DHCP: ----- DHCP Header -----
DHCP: Boot record type = 2 (Reply)
DHCP: Hardware address type = 1 (10M Ethernet)
DHCP: Hardware address length = 6 bytes
DHCP: Hops = 0
DHCP: Transaction id = 6019121F
DHCP: Elapsed boot time = 0 seconds
DHCP: Flags = 0000
DHCP: 0 = no broadcast
DHCP: Client self-assigned address = [0.0.0.0]
DHCP: Client address =[192.168.0.180]
DHCP: Next Server to use in bootstrap = [0.0.0.0]
DHCP: Relay Agent = [0.0.0.0]
DHCP: Client hardware address = 001234567890
DHCP: Host name = ""
DHCP: Boot file name = ""
DHCP: Vendor Information tag = 53825276
DHCP: Message Type = 2
DHCP: Address renewel interval = 345600 (seconds)
DHCP: Address rebinding interval = 604800 (seconds)
DHCP: Request IP Address leased time = 691200 (seconds)
DHCP: Sever IP Address = 【15】
DHCP: Subnet mask = 255.255.255.0
DHCP: Gateway address = [192.168.0.100]
DHCP: Domain Name Server address = [202.106.0.100]
求答案，解题思路！！！要详细！！！

Answer 1

这没什么思路，全靠对DHCP流程的了解
DHCP四个报文，discover，offer，Request，ACK

所以11是offer

对于DHCPoffer报文，可能采用单播，也可能采用广播，具体看flag
DHCP: 0 = no broadcast

这一行说明了采用的是单播
所以12（目的MAC地址）为001234567890

从DHCP: Client hardware address = 001234567890 找到

13（目的IP）为192.168.0.180

从DHCP: Client address =[192.168.0.180] 找到

14后面是68和67两个数字，这是DHCP使用的端口号，那么14肯定就是port

15，服务器的地址，那就是这个报文的源地址192.168.0.1

Answer 2

你是在校生吗？10年计算机等级考试时间是3月中旬，报名时间早过了。三级网络上机题就是用C语言编一道程序，所以说如果先过了二级，相对来说过三级更容易些。我10年也考网络，有什么不明白的可以继续问。

Answer 3

三级网络技术：全国计算机等级考试中三级的一种