如图1所示，DeviceA通过SwithC和DeviceB相连。在DeviceA上配置静态缺省路由可以与外部进行正常通信。同时，在DeviceA和DeviceB之间配置BFD会话来快速检测链路故障。
图1 配置静态BFD for IPv4静态路由组网图
配置思路- 在DeviceA和DeviceB上配置BFD会话，检测DeviceA和DeviceB之间的链路。配置DeviceA到外部的缺省路由并绑定BFD会话。
1.配置各接口IP地址（略）
2.配置DeviceA和DeviceB之间的BFD会话
# 在DeviceA上配置与DeviceB之间的BFD Session。
system-view [~DeviceA] bfd [*DeviceA-bfd] quit [*DeviceA] bfd aa bind peer-ip 1.1.1.2 [*DeviceA-bfd-session-aa] discriminator local 10 [*DeviceA-bfd-session-aa] discriminator remote 20 [*DeviceA-bfd-session-aa] commit [~DeviceA-bfd-session-aa] quit
# 在DeviceB上配置与DeviceA之间的BFD Session。
system-view [~DeviceB] bfd [*DeviceB-bfd] quit [*DeviceB] bfd bb bind peer-ip 1.1.1.1 [*DeviceB-bfd-session-bb] discriminator local 20 [*DeviceB-bfd-session-bb] discriminator remote 10 [*DeviceB-bfd-session-bb] commit [~DeviceB-bfd-session-bb] quit
3.配置静态缺省路由并绑定BFD会话
# 在DeviceA上配置到外部网络的静态缺省路由，并绑定BFD会话aa。
[~DeviceA] ip route-static 0.0.0.0 0 1.1.1.2 track bfd-session aa
4.验证配置结果
# 配置完成后，在DeviceA和DeviceB上执行display bfd session all命令，可以看到BFD会话已经建立，且状态为Up。在系统视图下执行display current-configuration | include bfd命令，可以看到静态路由已经绑定BFD会话。
以DeviceA上的显示为例。
[~DeviceA] display bfd session all
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
10 20 1.1.1.2 Up S_IP_PEER -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
S: Static session
D: Dynamic session
IP: IP session
IF: Single-hop session
PEER: Multi-hop session
AUTO: Automatically negotiated session
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
10 20 1.1.1.2 Up S_IP_PEER -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
[~DeviceA] display current-configuration | include bfd
bfd
bfd aa bind peer-ip 1.1.1.2
ip route-static 0.0.0.0 0.0.0.0 1.1.1.2 track bfd-session aa
# 在DeviceA上查看IP路由表，静态路由存在于路由表中。
[~DeviceA] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance, B - black hole route
------------------------------------------------------------------------------
Routing Table: Public
Destinations : 5 Routes : 5
Destination/Mask Proto Pre Cost Flags NextHop Interface
0.0.0.0/0 Static 60 0 RD 1.1.1.2 GigabitEthernet1/0/0
1.1.1.0/24 Direct 0 0 D 1.1.1.1 GigabitEthernet1/0/0
1.1.1.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet1/0/0
1.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet1/0/0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
# 对DeviceB的接口GE1/0/0执行shutdown命令模拟链路故障。
[~DeviceB] interface GigabitEthernet 1/0/0 [~DeviceB-GigabitEthernet1/0/0] shutdown
# 查看DeviceA的路由表，发现静态缺省路由0.0.0.0/0也不存在了。因为静态缺省路由绑定了BFD会话，当BFD检测到故障后，就会迅速通知所绑定的静态路由不可用。
[~DeviceA] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance, B - black hole route
------------------------------------------------------------------------------
Routing Table: Public
Destinations : 4 Routes : 4
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.0/24 Direct 0 0 D 1.1.1.1 GigabitEthernet1/0/0
1.1.1.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet1/0/0
1.1.1.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet1/0/0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
