如下图，路由器R1和R2之间有两条链路，路由器各接口以及回环接口已完成IP地址的配置：
R1各接口IP地址信息配置如下：
<R1>dis ip int b
*down: administratively down
!down: FIB overload down
^down: standby
(l): loopback
(s): spoofing
(d): Dampening Suppressed
The number of interface that is UP in Physical is 4
The number of interface that is DOWN in Physical is 8
The number of interface that is UP in Protocol is 4
The number of interface that is DOWN in Protocol is 8
Interface IP Address/Mask Physical Protocol
Ethernet0/0/0 12.1.1.1/24 up up
Ethernet0/0/1 21.1.1.1/24 up up
GigabitEthernet0/0/0 unassigned down down
GigabitEthernet0/0/1 unassigned down down
GigabitEthernet0/0/2 unassigned down down
GigabitEthernet0/0/3 unassigned down down
LoopBack0 1.1.1.1/24 up up(s)
NULL0 unassigned up up(s)
Serial0/0/0 unassigned down down
Serial0/0/1 unassigned down down
Serial0/0/2 unassigned down down
Serial0/0/3 unassigned down down
<R1>
R2各接口的IP地址信息配置如下：
<R2>dis ip int b
*down: administratively down
!down: FIB overload down
^down: standby
(l): loopback
(s): spoofing
(d): Dampening Suppressed
The number of interface that is UP in Physical is 4
The number of interface that is DOWN in Physical is 8
The number of interface that is UP in Protocol is 4
The number of interface that is DOWN in Protocol is 8
Interface IP Address/Mask Physical Protocol
Ethernet0/0/0 12.1.1.2/24 up up
Ethernet0/0/1 21.1.1.2/24 up up
GigabitEthernet0/0/0 unassigned down down
GigabitEthernet0/0/1 unassigned down down
GigabitEthernet0/0/2 unassigned down down
GigabitEthernet0/0/3 unassigned down down
LoopBack0 2.2.2.2/24 up up(s)
NULL0 unassigned up up(s)
Serial0/0/0 unassigned down down
Serial0/0/1 unassigned down down
Serial0/0/2 unassigned down down
Serial0/0/3 unassigned down down
<R2>
现在优选链路上配置BFD检测：
1.在R1和R2上配置静态路由以及优先级
# R1路由器上配置
[R1]ip route-static 2.2.2.0 255.255.255.0 12.1.1.2 preference 50 # 将路由优先级改为50 设置为优选路径
[R1]
[R1]ip route-static 2.2.2.0 255.255.255.0 21.1.1.2
[R1]
# R2路由器上配置
[R2]ip route-static 1.1.1.0 255.255.255.0 12.1.1.1 preference 50
[R2]ip route-static 1.1.1.0 255.255.255.0 21.1.1.1
[R2]
2.配置静态bfd
# R1上配置：
[R1]bfd # 全局使能bfd
[R1-bfd]quit
[R1]bfd mybfd01 bind peer-ip 12.1.1.2 source-ip 12.1.1.1
[R1-bfd-session-mybfd01]discriminator local 1 #本地标识 两台路由器的标识需要互为对称
[R1-bfd-session-mybfd01]discriminator remote 2
[R1-bfd-session-mybfd01]commit # 确认提交配置
[R1-bfd-session-mybfd01]quit
[R1]ip route-static 2.2.2.0 255.255.255.0 12.1.1.2 preference 50 ?
description Add or delete description of unicast static route
permanent Specifies route permanent
tag Specifies route tag
track Specify track object
<cr>
# 关联需要心跳检测的路由
[R1]ip route-static 2.2.2.0 255.255.255.0 12.1.1.2 preference 50 track bfd-session mybfd01
Info: Succeeded in modifying route.
[R1]
# R2上配置：
[R2]bfd
[R2-bfd]quit
[R2]bfd mybfd02 bind peer-ip 12.1.1.1 source-ip 12.1.1.2
[R2-bfd-session-mybfd02]dis
[R2-bfd-session-mybfd02]discriminator local 2
[R2-bfd-session-mybfd02]dis
[R2-bfd-session-mybfd02]discriminator re
[R2-bfd-session-mybfd02]discriminator remote 1
[R2-bfd-session-mybfd02]commit
[R2-bfd-session-mybfd02]quit
[R2]ip route-static 1.1.1.0 255.255.255.0 12.1.1.1 pre
[R2]ip route-static 1.1.1.0 255.255.255.0 12.1.1.1 preference 50 track bfd-session mybfd02
Info: Succeeded in modifying route.
[R2]
3.调试命令的使用
分别在R1和R2上查看bfd会话：
<R1>dis bfd session static
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
1 2 12.1.1.2 Up S_IP_PEER -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
<R1>dis bfd session static ver
<R1>dis bfd session static verbose
--------------------------------------------------------------------------------
Session MIndex : 256 (Multi Hop) State : Up Name : mybfd01
--------------------------------------------------------------------------------
Local Discriminator : 1 Remote Discriminator : 2
Session Detect Mode : Asynchronous Mode Without Echo Function
BFD Bind Type : Peer IP Address
Bind Session Type : Static
Bind Peer IP Address : 12.1.1.2
Bind Interface : -
Track Interface : -
Bind Source IP Address : 12.1.1.1
FSM Board Id : 0 TOS-EXP : 7 （报文优先级为7，优先传输）
Min Tx Interval (ms) : 1000 Min Rx Interval (ms) : 1000
Actual Tx Interval (ms): 1000 Actual Rx Interval (ms): 1000
Local Detect Multi : 3 Detect Interval (ms) : 3000
Echo Passive : Disable Acl Number : -
Destination Port : 3784 TTL : 254
Proc Interface Status : Disable Process PST : Disable
WTR Interval (ms) : - Local Demand Mode : Disable
Active Multi : 3
Last Local Diagnostic : No Diagnostic
Bind Application : No Application Bind
Session TX TmrID : 1035 Session Detect TmrID : 1036
Session Init TmrID : - Session WTR TmrID : -
Session Echo Tx TmrID : -
PDT Index : FSM-0 | RCV-0 | IF-0 | TOKEN-0
Session Description : -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
<R1>
<R1>
<R1>
<R2>dis bfd session static
--------------------------------------------------------------------------------
Local Remote PeerIpAddr State Type InterfaceName
--------------------------------------------------------------------------------
2 1 12.1.1.1 Up S_IP_PEER -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
<R2>dis bfd session static verbose
--------------------------------------------------------------------------------
Session MIndex : 256 (Multi Hop) State : Up Name : mybfd02
--------------------------------------------------------------------------------
Local Discriminator : 2 Remote Discriminator : 1
Session Detect Mode : Asynchronous Mode Without Echo Function
BFD Bind Type : Peer IP Address
Bind Session Type : Static
Bind Peer IP Address : 12.1.1.1
Bind Interface : -
Track Interface : -
Bind Source IP Address : 12.1.1.2
FSM Board Id : 0 TOS-EXP : 7
Min Tx Interval (ms) : 1000 Min Rx Interval (ms) : 1000
Actual Tx Interval (ms): 1000 Actual Rx Interval (ms): 1000
Local Detect Multi : 3 Detect Interval (ms) : 3000
Echo Passive : Disable Acl Number : -
Destination Port : 3784 TTL : 254
Proc Interface Status : Disable Process PST : Disable
WTR Interval (ms) : - Local Demand Mode : Disable
Active Multi : 3
Last Local Diagnostic : No Diagnostic
Bind Application : No Application Bind
Session TX TmrID : 1040 Session Detect TmrID : 1041
Session Init TmrID : - Session WTR TmrID : -
Session Echo Tx TmrID : -
PDT Index : FSM-0 | RCV-0 | IF-0 | TOKEN-0
Session Description : -
--------------------------------------------------------------------------------
Total UP/DOWN Session Number : 1/0
<R2>
注：TOS-EXP : 7 （报文优先级为7，优先传输）
然后在R1上抓包，可以看到BFD心跳报文信息：
由上图看出，BFD的端口号是UDP 3784，发送时间是1000ms，也就是1s，检测时间是3s。
4.测试
断开优选链路，进行测试，过程略。
