组网需求

如图1所示，SwitchA、SwitchB和SwitchC之间运行OSPF，SwitchA和SwitchB之间的交换机仅作透传功能。现在需要SwitchA和SwitchB能快速感应它们之间的链路状态，当链路SwitchA-SwitchB发生故障时，业务能快速切换到备份链路SwitchA-SwitchC-SwitchB上

说明

请确保该场景下互联接口的STP处于未使能状态。因为在使能STP的环形网络中，如果用交换机的VLANIF接口构建三层网络，会导致某个端口被阻塞，从而导致三层业务不能正常运行

配置思路

采用如下思路配置OSPF与BFD联动：

1. 在各交换机上配置OSPF基本功能，实现整个OSPF网络的互通。

2. 在各交换机上配置OSPF与BFD联动功能，实现当SwitchA和SwitchB之间的链路出现故障时快速的切换到备份链路。

操作步骤

配置各接口所属的VLAN

# 配置SwitchA。SwitchB和SwitchC的配置与SwitchA类似。

[zhongwanzhi]vlan batch 10 30
[zhongwanzhi]interface GigabitEthernet 0/0/1
[zhongwanzhi-GigabitEthernet0/0/1]port link-type trunk 
[zhongwanzhi-GigabitEthernet0/0/1]port trunk allow-pass vlan 10
[zhongwanzhi-GigabitEthernet0/0/1]quit
[zhongwanzhi]interface GigabitEthernet 0/0/2
[zhongwanzhi-GigabitEthernet0/0/2]port link-type tr	
[zhongwanzhi-GigabitEthernet0/0/2]port link-type trunk 
[zhongwanzhi-GigabitEthernet0/0/2]port trunk allow-pass vlan 30
[zhongwanzhi-GigabitEthernet0/0/2]quit

配置各VLANIF接口的IP地址

# 配置SwitchA。SwitchB和SwitchC的配置与SwitchA类似

[zhongwanzhi]interface Vlanif 30
[zhongwanzhi-Vlanif30]ip address 10.3.3.1 24
[zhongwanzhi-Vlanif30]quit
[zhongwanzhi]interface Vlanif 10
[zhongwanzhi-Vlanif10]ip address 10.1.1.1 24
[zhongwanzhi-Vlanif10]quit

配置OSPF基本功能

# 配置SwitchA、SwitchB和SwitchC的配置与SwitchA类似

[zhongwanzhi]ospf 1 router-id 10.10.10.1
[zhongwanzhi-ospf-1]area 0
[zhongwanzhi-ospf-1-area-0.0.0.0]network 10.1.1.0 0.0.0.255
[zhongwanzhi-ospf-1-area-0.0.0.0]network 10.3.3.0 0.0.0.255
[zhongwanzhi-ospf-1-area-0.0.0.0]quit
[zhongwanzhi-ospf-1]quit

# 配置完成后，执行命令display ospf peer，可以看到SwitchA，SwitchB和SwitchC之间互相建立了邻接关系。以SwitchA的显示结果为例

[zhongwanzhi]display ospf peer OSPF Process 1 with Router ID 10.10.10.1Neighbors Area 0.0.0.0 interface 10.1.1.1(Vlanif10)'s neighborsRouter ID: 10.10.10.3       Address: 10.1.1.2        State: Full  Mode:Nbr is  Master  Priority: 1DR: 10.1.1.1  BDR: 10.1.1.2  MTU: 0    Dead timer due in 34  sec Retrans timer interval: 5 Neighbor is up for 00:00:20     Authentication Sequence: [ 0 ] [zhongwanzhi]display ospf peerOSPF Process 1 with Router ID 10.10.10.1Neighbors Area 0.0.0.0 interface 10.1.1.1(Vlanif10)'s neighborsRouter ID: 10.10.10.3       Address: 10.1.1.2        State: Full  Mode:Nbr is  Master  Priority: 1DR: 10.1.1.1  BDR: 10.1.1.2  MTU: 0    Dead timer due in 34  sec Retrans timer interval: 5 Neighbor is up for 00:00:47     Authentication Sequence: [ 0 ] 

配置OSPF与BFD联动

# 在SwitchA上配置OSPF与BFD联动功能。SwitchB和SwitchC的配置与SwitchA类似。

[zhongwanzhi]bfd	
[zhongwanzhi-bfd]quit
[zhongwanzhi]ospf 1
[zhongwanzhi-ospf-1]bfd all-interfaces enable 
[zhongwanzhi-ospf-1]quit

# 配置完成后，在SwitchA或SwitchB、SwitchC上执行display ospf bfd session all命令，可以看到BFD会话的状态为Up。以SwitchA的显示为例。

[zhongwanzhi]display ospf bfd session all OSPF Process 1 with Router ID 10.10.10.1Area 0.0.0.0 interface 10.1.1.1(Vlanif10)'s BFD SessionsNeighborId:10.10.10.3       AreaId:0.0.0.0          Interface:Vlanif10      BFDState:up                 rx    :1000             tx       :1000          Multiplier:3                BFD Local Dis:8192      LocalIpAdd:10.1.1.1RemoteIpAdd:10.1.1.2        Diagnostic Info:No diagnostic information