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综合体第三题（DHCP报文分析）

news 来源：原创 2024/9/25 12:19:24

DHCP工作流程（一般情况下）

例二（无忧/22）

下图为DHCP客户机获取IP地址等配置信息时，使用Wareshark软件捕获报文中编号为2〜5的4条报文，图中对编号为3的报文进行了解析。分析图中的信息并补全图中①〜⑤处的信息

[1]192.168.1.36

[2]255.255.255.255

[3]offer

[]

pconfig/all用于获取参数的信息

DHCP工作流程（续约：执行ipconfig/renew）

例一

某公司网络DHCP服务器地址为192.168.0.2，可分配IP地址为192.168.0.6-192.168.0.254，缺省网关的地址为192.168.0.1，DNS服务器地址为192.168.0.2。网络中某客户机从服务器获取IP地址后，在客户机上执行ping命令的过程中，连续捕获的4条报文及对第4条报文的部分解析如下图所示。请补全图中空白处的信息。

编号	源IP地址	目的IP地址	报文摘要
1	192.168.0.10	192.168.0.1	Ping:Request
2	[1]	[2]	Ping:Reply
3	192.168.0.10	[3]	DHCP:Request, Type: Request
4	[4]	192.168.0.10	DHCP:Reply, Type:Ack
DHCP:----- DHCP Header ----- DHCP: Boot record type = 2 (Reply) DHCP: Hardware address type = 1 (10M Ethernet) DHCP: Hardware address length = 6 bytes DHCP: Client self-assigned address =[192.168.0.10] DHCP: Client address = [192.168.0.10] DHCP: Next Server to use in bootstrap = [0.0.0.0] DHCP: Relay Agent = [0.0.0.0] DHCP: Client hardware address = 001122334455 DHCP: VendorInformation tag = 63825363 DHCP: MessageType = 5 DHCP: Address renewel interval = 345600 (seconds) DHCP: Address rebinding interval = 604800 (seconds) DHCP: Request IP Address lease time = 691200 (seconds) DHCP: Subnet mask = 255.255.255.0 DHCP: Gateway address = [ [5]] DHCP: Domain Name Server address = [192.168.0.2]

[1]192.168.0.1

[2]192.168.0.10

[3]192.168.0.2

[4]192.168.0.2

[5]192.168.0.1

DHCP（释放后重获地址ipconfig/relesse和ipconfig/renew）

例一

（无忧/23）下图是在DHCP客户机上依次执行命令ipconfig /release和ipconfig /renew过程中，使用Wareshark软件捕获报文中的2条报文:图中对第2条报文进行了解析。

1.分析图中的信息并补全图中①〜⑤处的信息

[1][2]

我们可以观察到，这两幅图片“DHCP Discover”是一样的，【1】空指的是发送报文的ip，【2】空指的是接收报文的地址，正好对应【1】0.0.0.0 【2】255.255.255.255

[3]

[4]

Client MAC adress 指的是客户机的物理地址

通过这个图我们可以看出来客户机的ip地址192.168.1.1

[5]

例二

如下图所示，在某DHCP客户机上捕获了6个报文，并对第5条报文进行了解析。

编号		源IP地址			目的IP地址		报文摘要		报文捕获时间
1		192.168.0.1			192.168.0.36		DHCP:Request, Type:DHCP release		09:06:55
2		0.0.0.0			255.255.255.255		DHCP:Request, Type:DHCP discover		09:07:00
	3		192.168.0.36			255.255.255.255		DHCP:Reply, Type:DHCP offer		09:07:00
	4		0.0.0.0			255.255.255.255		DHCP:Request, Type:DHCP request		09:07:00
	5		192.168.0.36			255.255.255.255		DHCP:Reply, Type:DHCP ack		09:07:00
	6		192.168.0.1			192.168.0.47		WINS: C ID=33026 op=register name=xp		09:07:03
				DHCP: ----- DHCP Header ----- DHCP: Boot record type = 2 (Reply) DHCP: Hardware address type = 1 (10M Ethernet) DHCP: Hardware address length = 6 bytes DHCP: DHCP: Hops = 0 DHCP: Transaction id = 2219131D 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 = [192.168.0.1] DHCP: Next Server to use in bootstrap = [0.0.0.0] DHCP: Relay Agent = [0.0.0.0] DHCP: Client hardware address = 001122334455 DHCP: DHCP: Host name = "" DHCP: Boot file name = "" DHCP: DHCP: Vendor Information tag = 63825363 DHCP: Message Type = 5 (DHCP Ack) DHCP: Address renewel interval = 345600 (seconds) DHCP: Address rebinding interval = 604800 (seconds) DHCP: Request IP Address lease time = 691200 (seconds) DHCP: Subnet mask = 255.255.255.0 DHCP: Gateway address = [192.168.0.100] DHCP: Domain Name Server address = [202.106.0.20]

分析图中信息并回答下列问题。

（1）该客户机获取的IP地址是 [198.168.0.1]

我们可以观察到“Type:DHCP release”就因该明白对应的是第一个步骤左边的就是客户端地址。

（2）在DHCP服务器中设置的DNS服务器地址是 [202.106.0.20]，设置的路由器地址是 [192.168.0.100]。

“Domain Name Server”的缩写就是DSN（域名服务器地址，DNS服务器的ip地址）；“Gateway address ”就是网关地址，缺省路由（客户机直连的路由器）的ip地址。

（3）若该客户机由DHCP服务器分配固定的IP地址，则在新建保留时，需输入的MAC地址是 [001122334455]。

“Client hardware address” 指的就是客户机的物理地址（MAC地址）

（4）DHCP服务器的IP地址是 [192.168.0.36]。

我们可以观察到“Type:DHCP release”就因该明白对应的是第一个步骤左边的就是DHCP服务器的IP地址。

例三{无忧/4}

某公司网络DHCP服务器地址为192.168.0.2，可分配IP地址为192.168.0.6-192.168.0.254，缺省网关的地址为192.168.0.1。网络中某客户机从服务器获取IP地址后，在客户机上执行ping www.bupt.edu.cn命令的过程中，连续捕获的5条报文及对第5条报文的部分解析如下图所示。请补全图中空白处的信息。

编号		源IP地址		目的IP地址		报文摘要
1		192.168.0.6		192.168.0.3		Dns:Query
	2		[1]		[2]		Dns:Response
	3		192.168.0.6		114.255.40.66		Ping:Request
	4		192.168.0.6		192.168.0.2		DHCP:Request, Type: Request
	5		[3]		[4]		DHCP:Reply, Type:Ack
DHCP: ----- DHCP Header ----- DHCP: Boot record type = 2 (Reply) DHCP: Hardware address type = 1 (10M Ethernet) DHCP: Hardware address length = 6 bytes DHCP: Client self-assigned address = [192.168.0.6] DHCP: Client address = [192.168.0.6] DHCP: Next Server to use in bootstrap = [0.0.0.0] DHCP: Relay Agent = [0.0.0.0] DHCP: Client hardware address = 001122334455 DHCP: Vendor Information tag = 63825363 DHCP: Message Type = 5 DHCP: Address renewel interval = 345600 (seconds) DHCP: Address rebinding interval = 604800 (seconds) DHCP: Request IP Address lease time = 691200 (seconds) DHCP: Subnet mask = 255.255.255.0 DHCP: Gateway address = [192.168.0.1] DHCP: Domain Name Server address = [ [5]]