305 lines
9.4 KiB
Markdown
305 lines
9.4 KiB
Markdown
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# BFD
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### 一、BFD概述
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1. Bidirectional Forwarding Detection
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> 双向转发检测
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2. BFD技术背景
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1. 现网中存在的问题
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- 不能快速有效的发现网络设备或链路出现的故障
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- 不能以毫秒级的速度发现网络问题
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- 协议自身的报文检测机制一般都大于1秒
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2. 解决方案：
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- 需要一种专门用于快速检测设备或链路的协议：BFD协议产生
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3. BFD的作用
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- 专门用于发送超小和超快的检测数据包，以毫秒级进行发送，快速检测链路的故障，改善网络性能
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- 当发现链路故障时，通知相关的设备和协议进行处理，快速恢复通信，保证网络可靠性
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4. BFD的优点
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- 对任何介质、任何协议层进行实时且快速的检测
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5. BFD会话建立方式
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- BFD会话的建立有：静态建立、动态建立两种方式
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- 静态建立BFD会话：手工配置BFD会话参数（手工配置：本地标识符和远端标识符）
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- 动态建立BFD会话：动态分配本地标识符、自学习远端标识符
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- 静态和动态的主要区别：本地标识符和远端标识符配置方式不同
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6. BFD检测机制
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- 两个设备建立BFD会话，链路两端周期性发送BFD控制报文，如果一端在既定的时间内没有收到BFD控制报文，则认为路径上发生了故障。
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7. BFD会话常见参数的缺省配置
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| 参数 | 缺省值 |
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| ------------ | -------- |
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| 发送间隔 | 1000毫秒 |
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| 接收间隔 | 1000毫秒 |
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| 本地检测倍数 | 3 |
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### 二、BFD和静态路由联动
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- **需求**
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- 实现PC1 和PC2的互联互通
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- 实现BFD和静态路由联动
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- **配置步骤**
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1. 配置PC的IP地址，掩码，网关
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2. 配置路由器的接口IP地址
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3. 配置静态路由和浮动路由
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4. 配置BFD
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5. 配置BFD和静态路由联动
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6. 验证与测试
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- **配置命令**
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- 第一步：配置PC的接口IP地址
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- 第二步：配置路由器的接口IP地址
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- 第三步：配置静态路由和浮动路由
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- R1配置浮动路由
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```
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[R1]ip route-static 192.168.2.0 24 192.168.12.2 ：主路由
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[R1]ip route-static 192.168.2.0 24 192.168.13.3 preference 70 ：浮动路由
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```
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> R1去往24.0网段，要做BFD[R1]ip route-static 192.168.24.0 24 192.168.12.2
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- R2配置静态路由
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```
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[R2]ip route-static 192.168.1.0 24 192.168.12.1
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[R2]ip route-static 192.168.2.0 24 192.168.24.4
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```
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- R3配置静态路由
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```
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[R3]ip route-static 192.168.1.0 24 192.168.13.1
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[R3]ip route-static 192.168.2.0 24 192.168.34.4
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```
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- R4配置浮动路由
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```
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[R4]ip route-static 192.168.1.0 24 192.168.24.2
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[R4]ip route-static 192.168.1.0 24 192.168.34.3 preference 70
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```
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> R4去往12.0网段，要做BFD[R4]ip route-static 192.168.12.0 24 192.168.24.2
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- 第四步：配置BFD
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- R1的配置
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```
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[R1]bfd
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[R1-bfd]quit
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[R1]bfd ntd bind peer-ip 192.168.24.4
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[R1-bfd-session-ntd]discriminator local 1
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[R1-bfd-session-ntd]discriminator remote 4
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[R1-bfd-session-ntd]min-tx-interval 10
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[R1-bfd-session-ntd]min-rx-interval 10
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[R1-bfd-session-ntd]commit
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[R1-bfd-session-ntd]quit
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```
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- R4的配置
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```
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[R4]bfd
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[R4-bfd]quit
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[R4]bfd ntd bind peer-ip 192.168.12.1
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[R4-bfd-session-ntd]discriminator local 4
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[R4-bfd-session-ntd]discriminator remote 1
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[R4-bfd-session-ntd]min-tx-interval 10
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[R4-bfd-session-ntd]min-rx-interval 10
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[R4-bfd-session-ntd]commit
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```
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- 第五步：配置BFD和静态路由联动
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- R1
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```
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[R1]ip route-static 192.168.2.0 24 192.168.12.2 track bfd-session ntd2308
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```
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- 第六步：验证与测试
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- R1
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```
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<R1>display bfd session all
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```
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> 将R2和R4之间的链路断开，验证浮动路由是否切换
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>
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> 确保PC1和PC2能够正常通信，不因链路中断，而导致网络不可达
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### 三、VRRP和BFD联动实验
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- **需求**
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- 部署VRRP，让SW1成为备份组10的-Master设备（vlan10的主网关）
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- 让SW2成为备份组10的-Backup设备（vlan10的备份网关）
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- 部署VRRP和BFD联动可以解决的问题：
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- 在VRRP中当SW1-主网关，出现故障的时候，备份网关SW2需要等待3秒后，才可以升级为新的主网关，承担流量转发任务。
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- 3秒对有些企业网络来说是不可以接受的，我们需要实现VRRP主备设备更加快速的切换（毫秒级故障切换）
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- **解决方案**
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- 在运行VRRP网络设备上(SW1/SW2)运行BFD协议
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- 在SW1和SW2之间建立BFD会话，通过BFD协议快速检测和感知设备或链路故障
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- 在SW2中配置VRRP和BFD联动，当SW1-主网关出现故障的时候，BFD会话会Down
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- 此时BFD协议会通知备份网关SW2，立即将VRRP优先级调高，已实现SW2快速成为主网关
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- **配置步骤**
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- 第一步：配置PC的IP地址，掩码，网关
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- 第二步：配置sw3交换机的vlan，端口加vlan 配trunk
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- 第三步：SW1和SW2配置vrrp-热备
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1. 创建vlan
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2. 配置vlanif接口地址
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3. 配置vrrp 备份组，配置虚拟IP
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4. 配置优先级
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5. 交换机互联接口配置trunk
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- 第四步：配置SW1和SW2的BFD会话
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1. 开启BFD功能
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2. 创建BFD会话
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3. 配置本地标识符
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4. 配置远端标识符
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5. 提交
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- 第五步：配置VRRP和BFD联动
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- 配置VRRP和BFD联动，跟踪BFD会话，一旦发现BFD会话down掉，SW2的VRRP的优先级会在原来的基础上增加60，让SW2快速的成为Master设备
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- 第六步：模拟故障，验证BFD
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- **配置命令**
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- 第一步：配置PC的IP地址，掩码，网关
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- 第二步：配置sw3交换机的vlan，端口加vlan 配trunk
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- SW3配置
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```
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[SW3]vlan 10
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[SW3-vlan10]quit
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[SW3]port-group group-member g0/0/1 g0/0/2
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[SW3-port-group]port link-type access
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[SW3-port-group]port default vlan 10
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[SW3-port-group]quit
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[SW3]port-group group-member g0/0/3 g0/0/4
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[SW3-port-group]port link-type trunk
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[SW3-port-group]port trunk allow-pass vlan all
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```
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- 第三步：SW1和SW2配置vrrp-热备
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- SW1配置
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```
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[SW1]vlan 10
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[SW1-vlan10]quit
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[SW1]int g0/0/1
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[SW1-G0/0/1]port link-type trunk
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[SW1-G0/0/1]port trunk allow-pass vlan all
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[SW1-G0/0/1]quit
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[SW1]int vlanif 10
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[SW1-Vlanif10]ip address 192.168.10.251 24
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[SW1-Vlanif10]vrrp vrid 10 virtual-ip 192.168.10.254
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[SW1-Vlanif10]vrrp vrid 10 priority 130
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```
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- SW2配置
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```
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[SW2]vlan 10
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[SW2-vlan10]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
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[SW2-G0/0/1]quit
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[SW2]int vlanif 10
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[SW2-Vlanif10]ip address 192.168.10.252 24
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[SW2-Vlanif10]vrrp vrid 10 virtual-ip 192.168.10.254
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```
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- 第四步：配置SW1和SW2的BFD会话
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- SW1配置
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```
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[SW1]bfd //开启BFD功能
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[SW1-bfd]quit //退出
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[SW1]bfd tedu bind peer-ip 192.168.10.252 //在系统视图下创建BFD会话，绑定对端IP地址
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[SW1-bfd-session-tedu]discriminator local 1 //配置本地标识符
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[SW1-bfd-session-tedu]discriminator remote 2 //配置远端标识符
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[SW1-bfd-session-tedu]min-rx-interval 100 //配置接收报文间隔时间（100毫秒）
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[SW1-bfd-session-tedu]min-tx-interval 100 //配置发送报文间隔时间（100毫秒）
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[SW1-bfd-session-tedu]commit //提交
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```
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- SW2
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```
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[SW2]bfd //开启BFD功能
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[SW2-bfd]quit
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[SW2]bfd tedu bind peer-ip 192.168.10.251 //创建BFD会话，绑定对端IP地址
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[SW2-bfd-session-tedu]discriminator local 2 //本地标识符为2
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[SW2-bfd-session-tedu]discriminator remote 1 //远端标识符为1
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[SW2-bfd-session-tedu]min-rx-interval 100 //接受报文间隔时间100毫秒
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[SW2-bfd-session-tedu]min-tx-interval 100 //发送报文间隔时间100毫秒
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[SW2-bfd-session-tedu]commit //提交
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```
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- 第五步：在SW2上配置VRRP和BFD联动
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```
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[SW2]int vlanif 10
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[SW2-Vlanif10]vrrp vrid 10 track bfd-session 2 increased 60
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```
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> 配置VRRP和BFD联动，跟踪BFD会话，一旦发现BFD会话down掉，就让SW2的VRRP的优先级在原来的基础上增加60，让SW2快速的成为Master设备
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- 第六步：模拟SW1故障，在SW2中验证BFD和VRRP联动
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- SW2
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```
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[SW2]display vrrp
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Vlanif10 | Virtual Router 10
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State : Master
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Virtual IP : 192.168.10.254
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Master IP : 192.168.10.252
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PriorityRun : 160
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PriorityConfig : 100
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MasterPriority : 160
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Preempt : YES Delay Time : 0 s
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TimerRun : 1 s
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TimerConfig : 1 s
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Auth type : NONE
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Virtual MAC : 0000-5e00-010a
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Check TTL : YES
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Config type : normal-vrrp
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Track BFD : 2 Priority increased : 60 BFD-session state : DOWN // 重点看这条
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Create time : 2022-12-29 17:32:15 UTC-08:00
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Last change time : 2022-12-29 17:50:00 UTC-08:00
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