如下图为一个小型网络拓扑图，在核心交换机与路由器间设置BFD单跳检测三层链路。

具体配置如下：

[S1]bfd

[S1-bfd]q 

[S1]bfd r1 bind peer-ip 10.255.255.254 interface Vlanif 100

[S1-bfd-session-r1]discriminator local 1

[S1-bfd-session-r1]discriminator remote 2

[S1-bfd-session-r1]commit

---------------

[R1]bfd

[R1-bfd]q

[R1]bfd s1 bind peer-ip 10.255.255.1 interface GigabitEthernet 0/0/0

[R1-bfd-session-s1]discriminator local 2

[R1-bfd-session-s1]discriminator remote 1

[R1-bfd-session-s1]commit

=============

查看正常状态

[S1-bfd-session-r1]dis bf se all

--------------------------------------------------------------------------------

Local Remote     PeerIpAddr      State     Type        InterfaceName           

--------------------------------------------------------------------------------

1     2          10.255.255.254  Up        S_IP_IF     Vlanif100               

--------------------------------------------------------------------------------

     Total UP/DOWN Session Number : 1/0

---------------------

[R1]display bfd session all

--------------------------------------------------------------------------------

Local Remote     PeerIpAddr      State     Type        InterfaceName           

--------------------------------------------------------------------------------

2     1          10.255.255.1    Up        S_IP_IF     GigabitEthernet0/0/0    

--------------------------------------------------------------------------------

     Total UP/DOWN Session Number : 1/0

模拟连通失败状态（关闭交换机GE0/0/1接口）

[R1]display bfd session all verbose

--------------------------------------------------------------------------------

Session MIndex : 256       (One Hop) State : Down      Name : s1            

--------------------------------------------------------------------------------

  Local Discriminator    : 2                Remote Discriminator   : 1        

  Session Detect Mode    : Asynchronous Mode Without Echo Function            

  BFD Bind Type          : Interface(GigabitEthernet0/0/0)                    

  Bind Session Type      : Static   

  Bind Peer IP Address   : 10.255.255.1                                        

  NextHop Ip Address     : 10.255.255.1                                       

  Bind Interface         : GigabitEthernet0/0/0                               

  FSM Board Id           : 0                TOS-EXP                : 7        

  Min Tx Interval (ms)   : 1000             Min Rx Interval (ms)   : 1000     

  Actual Tx Interval (ms): 14499            Actual Rx Interval (ms): 14499    

  Local Detect Multi     : 3                Detect Interval (ms)   : -        

  Echo Passive           : Disable          Acl Number             : -        

  Destination Port       : 3784             TTL                    : 255      

  Proc Interface Status  : Disable          Process PST            : Disable  

  WTR Interval (ms)      : -        

  Active Multi           : 3        

  Last Local Diagnostic  : Control Detection Time Expired                     

  Bind Application       : No Application Bind

  Session TX TmrID       : 1036             Session Detect TmrID   : -        

  Session Init TmrID     : -                Session WTR TmrID      : -        

  Session Echo Tx TmrID  : -        

[R1]

===============

配置文件

<R1>dis cu

[V200R003C00]

#

 sysname R1

#

bfd

#

interface GigabitEthernet0/0/0

 ip address 10.255.255.254 255.255.255.0

#

bfd s1 bind peer-ip 10.255.255.1 interface GigabitEthernet0/0/0

 discriminator local 2

 discriminator remote 1

 commit

#

return

<R1>

--------------------

<S1>dis cu

#

sysname S1

#

vlan batch 100

#

bfd

#

interface Vlanif100

 ip address 10.255.255.1 255.255.255.0

#

interface GigabitEthernet0/0/1

 shutdown

 port link-type trunk

 port trunk pvid vlan 100

 port trunk allow-pass vlan 2 to 4094

#

interface GigabitEthernet0/0/2

#

interface NULL0

#

bfd r1 bind peer-ip 10.255.255.254 interface Vlanif100

 discriminator local 1

 discriminator remote 2

 commit

#

return