409 lines
14 KiB
Markdown
409 lines
14 KiB
Markdown
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# DHCP
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### 一、DHCP概述
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1. **DHCP是什么**
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- DHCP：Dynamic Host Configuration Protocol ：动态主机配置协议
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- DHCP是一种集中对用户IP地址进行动态管理和配置的技术
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2. **DHCP的作用**
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- 作用：实现IP地址的动态分配和集中管理
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- 优势：避免手工配置IP地址，提高工作效率，避免出错，且能快速适应网络的变化
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3. **DHCP角色**
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- DHCP客户端：需要获取IP地址的设备，如：计算机、服务器、手机、IP电话等
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- DHCP服务器：负责为DHCP客户端分配IP地址等网络参数的设备
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- DHCP 中继（中转站-可选）：负责DHCP服务器和DHCP客户端之间的DHCP报文（房地产中介公司）
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> 企业网络中一般不需要部署DHCP中继
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### 二、DHCP服务器给首次接入网络的客户端分配网络参数的工作原理
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1. **发现阶段**：客户端广播发送DHCP Discover报文（DHCP发现报文,客户端找DHCP服务器，请求IP地址）
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2. **提供阶段**：服务器收到客户端发的报文后，会单播回复DHCP Offer报文（DHCP回应报文,服务器给客户端发IP地址、网关、DNS等）
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3. **选择阶段**：客户端收到Offer报文后，会再次广播发送DHCP Request报文（DHCP请求报文,客户端广播告知所有的服务器，选择了某某IP地址）
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4. **确认阶段**：服务器收到客户端发报文后，会单播回复DHCP ACK报文（DHCP确认报文，确认分配结果，只有发了ACK报文，客户端才可以使用IP）
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### 三、基于全局的DHCP实验
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- **需求**
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> PC1/PC2能够自动获取IP地址、网关、DNS
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- **配置步骤**
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- 第一步：在系统视图下开启DHCP功能
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- 第二步：配置IP地址池
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- 创建IP地址池
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- 配置可分配的IP地址段
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- 配置网关地址
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- 配置DNS地址
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- 配置租期
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- 第三步：配置R1路由器接口的IP地址
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- 这个接口接收客户端发的报文，这个接口的IP地址，即客户端的网关地址
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- 在这个接口下开启基于全局的DHCP功能
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- 第四步：验证结果
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- **配置命令**
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- R1的配置
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```
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[R1]dhcp enable //开启DHCP功能
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[R1]ip pool tedu //创建IP地址池
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[R1-ip-pool-tedu]network 192.168.1.0 mask 24 //配置可分配的地址段
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[R1-ip-pool-tedu]gateway-list 192.168.1.254 //配置网关地址
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[R1-ip-pool-tedu]dns-list 8.8.8.8 //配置DNS地址
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[R1-ip-pool-tedu]lease day 1 //配置租期
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[R1-ip-pool-tedu]quit
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[R1]int g0/0/0
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[R1-G0/0/0]ip address 192.168.1.254 24 //此接口IP地址和网关地址一致
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[R1-G0/0/0]dhcp select global //在接口下开启基于全局的DHCP
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```
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- 验证与测试
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> PC1和PC2选择获取地址的方式为DHCP
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> 然后PC1和PC2在命令行中，使用ipconfig 命令查看IP地址
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- 数据抓包
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- 配置地址排除
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```
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[R1]ip pool tedu
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[R1-ip-pool-tedu]excluded-ip-address 192.168.1.250 192.168.1.253 //在基于全局的IP地址池中做地址排除,排除的IP地址不做dhcp分发
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```
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- 查看IP地址池
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```
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<R1>display ip pool name tedu all //查看全局IP地址池中全部地址信息
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<R1>display ip pool name tedu used //查看全局IP地址池中已分发的IP地址
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```
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### 四、基于接口的DHCP实验
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- **需求**
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> PC1/PC2能够自动获取IP地址、网关、DNS
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- **配置步骤**
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- 第一步：在系统视图下开启DHCP功能
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- 第二步：配置基于接口的DHCP
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- 配置接口的IP地址和掩码
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- 在接口下开启基于接口的DHCP功能
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- 在接口下配置DNS地址
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- 在接口下配置租期
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- **配置命令**
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- R1配置
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```
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[R1]dhcp enable //开启dhcp功能
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[R1]int g0/0/0
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[R1-G0/0/0]ip address 192.168.1.254 24
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[R1-G0/0/0]dhcp select interface //开启基于接口的dhcp 功能
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[R1-G0/0/0]dhcp server dns-list 8.8.8.8
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[R1-G0/0/0]dhcp server lease day 1
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```
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- **验证与测试**
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> PC1和PC2选择获取地址的方式为DHCP
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> 然后PC1和PC2在命令行中，使用ipconfig 命令查看IP地址
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### 五、DHCP中继代理原理
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- **问题**
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> 当客户机和DHCP服务器不在一个广播域时，DHCP服务器无法接收到客户机的DHCP discover广播数据包，客户机就无法获得IP地
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- **解决**
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> 在客户机所在的广播域中，寻找一台路由器，这台路由器一个端口在客户机所在的广播域，另外一个端口在DHCP服务器所在的广播域，让这台路由器主动接收客户机的DHCP discover数据包，然后由这台路由器代替客户机向DHCP服务器申请IP地址，得到地址后，再把这个地址交给客户机，这台服务器称之为DHCP中继代理服务器
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- **DHCP中继实验**
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- **需求**
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- 希望PC1/PC2自动获取到IP地址，网关、DNS等网络参数
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- Server1 服务器手工配置一个静态IP地址，192.168.10.253，这个地址是专门给服务器使用的，所以这个地址不能通过DHCP分发，避免IP地址冲突
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- **配置步骤**
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- 第一步：配置R2-DHCP服务器
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1. 在系统视图下开启DHCP功能
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2. 在R2-DHCP服务器中配置基于全局的DHCP
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- 创建IP地址池:ntd
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- 定义网段：192.168.10.0/24
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- 定义网关:192.168.10.254
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- 定于DNS：8.8.8.8
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- 定义排除地址：192.168.10.253 这个IP地址不做DHCP分发
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3. 在接口上配置IP地址，开启基于全局的dhcp
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- 第二步：配置DHCP中继
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1. R1中继设备开启DHCP功能
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2. 配置R1中继设备的接口IP地址
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3. 在R1设备连接客户端的接口上开启DHCP中继，指向DHCP服务器:192.168.20.20
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- 第三步：配置静态路由
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- 在R2配置去往192.168.10.0网段的路由，下一跳为192.168.20.10
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- 第四步：验证与测试
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- **配置命令**
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- 第一步：配置DHCP服务器
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- DHCP服务器配置
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```
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[R2-DHCP]dhcp enable //开启dhcp 功能
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[R2-DHCP]ip pool ntd //创建IP地址池
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[R2-DHCP-ip-pool-ntd]network 192.168.10.0 mask 24
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[R2-DHCP-ip-pool-ntd]gateway-list 192.168.10.254
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[R2-DHCP-ip-pool-ntd]dns-list 8.8.8.8
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[R2-DHCP-ip-pool-ntd]excluded-ip-address 192.168.10.253
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[R2-DHCP-ip-pool-ntd]quit
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[R2-DHCP]int g0/0/0
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[R2-DHCP-GigabitEthernet0/0/0]ip add 192.168.20.20 24
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[R2-DHCP-GigabitEthernet0/0/0]dhcp select global
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```
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- 第二步：配置DHCP中继
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```
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[R1-zj]dhcp enable
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[R1-zj]int g0/0/0
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[R1-zj-G0/0/0]ip add 192.168.20.10 24
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[R1-zj-G0/0/0]int g0/0/1
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[R1-zj-G0/0/1]ip add 192.168.10.254 24
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[R1-zj-G0/0/1]dhcp select relay //在接口上开启dhcp中继功能
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[R1-zj-G0/0/1]dhcp relay server-ip 192.168.20.2 //指定dhcp服务器的IP地址
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```
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- 第三步：在DHCP服务器上配置去往中继设备的回程路由
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```
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[R2-DHCP]ip route-static 192.168.10.0 24 192.168.20.10
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```
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- 第四步：验证与测试
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```
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在PC1和PC2中设置IP地址的获取方式为DHCP
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在PC1和PC2中命令行中输入命令
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```
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- **经验证发现**
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```
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PC1的IP地址是192.168.10.252
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PC2的IP地址是192.168.10.251
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192.168.10.253这个地址，已经被排除，没有被DHCP分发
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```
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### 六、三层交换机部署DHCP
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- **需求**
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> vlan10和vlan20的pc自动获取IP地址
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- **配置步骤**
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- 第一步：在sw1部署dhcp
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1. 创建vlan
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2. 配置trunk链路-交换机互联接口做trunk
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3. 配置vlanif 虚接口地址--每个vlan的网关地址
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4. 开启dhcp 功能
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5. 创建IP地址池
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- 定义网段
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- 定义网关
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- 定义dns
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6. 在vlanif 虚接口下，开启dhcp select global
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- 第二步：配置sw2和sw3接入层交换机
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1. 创建vlan
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2. 接口加入vlan,交换机和pc互联的接口做access
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3. 交换机和交换机互联的接口做trunk
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- 第三步：验证与测试
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- **配置命令**
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- 第一步：在sw1部署dhcp
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- DHCP服务器配置
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```
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[SW1-DHCP]vlan batch 10 20
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[SW1-DHCP]port-group group-member g0/0/1 g0/0/2
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[SW1-DHCP-port-group]port link-type trunk
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[SW1-DHCP-port-group]port trunk allow-pass vlan all
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[SW1-DHCP-port-group]quit
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[SW1-DHCP]ip pool vlan10
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[SW1-DHCP-ip-pool-vlan10]network 192.168.10.0 mask 24
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[SW1-DHCP-ip-pool-vlan10]gateway-list 192.168.10.254
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[SW1-DHCP-ip-pool-vlan10]dns-list 8.8.8.8
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[SW1-DHCP-ip-pool-vlan10]quit
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[SW1-DHCP]ip pool vlan20
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[SW1-DHCP-ip-pool-vlan20]network 192.168.20.0 mask 24
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[SW1-DHCP-ip-pool-vlan20]gateway-list 192.168.20.254
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[SW1-DHCP-ip-pool-vlan20]dns-list 8.8.8.8
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[SW1-DHCP-ip-pool-vlan20]quit
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[SW1-DHCP]dhcp enable
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[SW1-DHCP]int vlanif 10
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[SW1-DHCP-Vlanif10]ip address 192.168.10.254 24
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[SW1-DHCP-Vlanif10]dhcp select global
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[SW1-DHCP-Vlanif10]int vlanif 20
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[SW1-DHCP-Vlanif20]ip address 192.168.20.254 24
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[SW1-DHCP-Vlanif20]dhcp select global
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```
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- 第二步：配置sw2和sw3接入层交换机
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- SW2配置
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```
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[SW2]vlan batch 10 20
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[SW2]port-group group-member g0/0/2 g0/0/3
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[SW2-port-group]port link-type access
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[SW2-port-group]port default vlan 10
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[SW2-port-group]quit
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[SW2]int g0/0/1
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[SW2-G0/0/1]port link-type trunk
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[SW2-G0/0/1]port trunk allow-pass vlan all
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
- SW3配置
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW3]vlan batch 10 20
|
|||
|
|
[SW3]port-group group-member g0/0/2 g0/0/3
|
|||
|
|
[SW3-port-group]port link-type access
|
|||
|
|
[SW3-port-group]port default vlan 20
|
|||
|
|
[SW3-port-group]quit
|
|||
|
|
[SW3]int g0/0/1
|
|||
|
|
[SW3-G0/0/1]port link-type trunk
|
|||
|
|
[SW3-G0/0/1]port trunk allow-pass vlan all
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
- 第三步：验证与测试
|
|||
|
|
|
|||
|
|
- 在PC1和PC2中设置IP地址的获取方式为DHCP
|
|||
|
|
|
|||
|
|
- 在PC1和PC2中命令行中输入命令
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
ipconfig /release //释放当前IP地址
|
|||
|
|
ipconfig /renew //更新IP地址（获取IP地址）
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
<SW1-DHCP>display ip pool name vlan10 all //查看地址池中全部IP信息
|
|||
|
|
<SW1-DHCP>display ip pool name vlan10 used //查看地址中已使用的IP地址
|
|||
|
|
<SW1-DHCP>display ip pool name vlan20 all //查看地址池中全部IP信息
|
|||
|
|
<SW1-DHCP>display ip pool name vlan20 used //查看地址中已使用的IP地址
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
<S3>reset ip pool name vlan10 192.168.10.253回收已分配的IP地址
|
|||
|
|
<S3>reset ip pool name vlan10 all
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
### 七、租期
|
|||
|
|
|
|||
|
|
> 1）租期T1:
|
|||
|
|
> 当IP地址的租用时间到达50%时，客户机会以单播方式向服务器发送Request 请求报文，请求更新IP地址租期。
|
|||
|
|
> DHCP 服务器如果回复DHCP ACK确认报文给客户机，代表租期更新成功，从0开始
|
|||
|
|
|
|||
|
|
> 2）租期T2
|
|||
|
|
> 如果DHCP服务器一直没有回应，那么在IP地址的租用时间到达87.5%时，客户机会以广播方式向服务器发送Request 请求报文，请求更新IP地址租期
|
|||
|
|
> DHCP服务器如果回复DHCP ACK 确认报文给客户机，代表租期更新成功，从0开始
|
|||
|
|
|
|||
|
|
1. **access接口恢复默认配置（缺省配置）**
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW1]vlan batch 10 20
|
|||
|
|
[SW1]interface g0/0/1
|
|||
|
|
[SW1-GigabitEthernet0/0/1]port link-type access
|
|||
|
|
[SW1-GigabitEthernet0/0/1]port default vlan 10
|
|||
|
|
[SW1-GigabitEthernet0/0/1]port link-type trunk //将接口模式修改为trunk（失败）
|
|||
|
|
Error: Please renew the default configurations. ：错误：请更新默认配置
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
- 如何解决：如何恢复接口上VLAN的缺省配置
|
|||
|
|
|
|||
|
|
- 第一种方法
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW1-GigabitEthernet0/0/1]port default vlan 1 //接口pvid恢复为vlan1
|
|||
|
|
[SW1-GigabitEthernet0/0/1]port link-type trunk //将接口模式修改为trunk（成功）
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
- 第二种方法
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW1-GigabitEthernet0/0/1]undo port default vlan //恢复接口上VLAN的缺省配置
|
|||
|
|
[SW1-GigabitEthernet0/0/1]port link-type trunk //将接口模式修改为trunk（成功）
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
2. **trunk接口恢复默认配置（缺省配置）**
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW1]vlan batch 10 20
|
|||
|
|
[SW1]interface g0/0/1
|
|||
|
|
[SW1-G0/0/1]port link-type trunk
|
|||
|
|
[SW1-G0/0/1]port trunk allow-pass vlan 10 20
|
|||
|
|
[SW1-G0/0/1]port link-type access //将接口模式修改为access（失败）
|
|||
|
|
Error: Please renew the default configurations. ：错误：请更新默认配置
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
- 如何解决：如何恢复接口上VLAN的缺省配置
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW1-G0/0/1]undo port trunk allow-pass vlan 10 20 //恢复默认
|
|||
|
|
[SW1-G0/0/1]port link-type access //将接口模式修改为access（成功）
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
- 备注：
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW1-G0/0/1]undo port trunk allow-pass vlan all //删除所有vlan
|
|||
|
|
[SW1-G0/0/1]port link-type access //无法修改报错
|
|||
|
|
Error: Please renew the default configurations.
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
- 如何解决：恢复默认配置： undo port trunk allow-pass vlan all 的时候把所有vlan 都干掉了
|
|||
|
|
所以我们要恢复vlan1
|
|||
|
|
|
|||
|
|
- 第一种方法
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW1-G0/0/1]undo port trunk allow-pass vlan 2 to 4094 //只删除2 to 4094 不删除vlan1
|
|||
|
|
[SW1-G0/0/1]port link-type access //修改成功
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
- 第二种方法
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
[SW1-G0/0/1]undo port trunk allow-pass vlan all //删除所有vlan
|
|||
|
|
[SW1-G0/0/1]port trunk allow-pass vlan 1 //补上vlan1,恢复默认
|
|||
|
|
[SW1-G0/0/1]port link-type access //修改成功
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
|