二层链路配置一定配置缺省的BFD组播IP地址（可采用默认组播IP地址，所有设备组播IP需要一样）且指定本端设备的出接口

    如下图：

    在交换机S1、S2、S3之间设置BFD二层检测

 

[s3]bfd  #全局开启BFD功能

[s3-bfd]q

[s3]

[s3]bfd s1 bind peer-ip default-ip  interface GigabitEthernet 0/0/1

 # 设置名为S1的BFD会话并绑定对端地址（组播地址）及指定本段出接口

[s3-bfd-session-s1]discriminator local 31  #设置本地标识符

[s3-bfd-session-s1]discriminator remote 13  #设置对端标识符

[s3-bfd-session-s1]commit  #提交bfd会话，否则不生效。

[s3]bfd s2 bind  peer-ip default-ip interface g 0/0/2

[s3-bfd-session-s2]discriminator local 21

[s3-bfd-session-s2]discriminator remote 12

[s3-bfd-session-s2]commit

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

[s2]bfd

[s2-bfd]q

[s2]

[s2]bfd s1 bind peer-ip default-ip  interface GigabitEthernet 0/0/1

[s2-bfd-session-s1]discriminator local 21

[s2-bfd-session-s1]discriminator remote 12

[s2-bfd-session-s1]commit

[s2]bfd s3 bind  peer-ip default-ip interface g 0/0/2

[s2-bfd-session-s3]discriminator local 23

[s2-bfd-session-s3]discriminator remote 32

[s2-bfd-session-s3]commit

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

[s3]bfd

[s3-bfd]q

[s3]

[s3]bfd s1 bind peer-ip default-ip  interface GigabitEthernet 0/0/1

[s3-bfd-session-s1]discriminator local 31

[s3-bfd-session-s1]discriminator remote 13

[s3-bfd-session-s1]commit

[s3]bfd s2 bind  peer-ip default-ip interface g 0/0/2

[s3-bfd-session-s2]discriminator local 21

[s3-bfd-session-s2]discriminator remote 12

[s3-bfd-session-s2]commit

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

[s1]bfd

[s1-bfd]q

[s1]

[s1]bfd s2 bind peer-ip default-ip  interface GigabitEthernet 0/0/1

[s1-bfd-session-s2]discriminator local 12

[s1-bfd-session-s2]discriminator remote 21

[s1-bfd-session-s2]commit

[s1]bfd s3 bind  peer-ip default-ip interface g 0/0/2

[s1-bfd-session-s3]discriminator local 13

[s1-bfd-session-s3]discriminator remote 31

[s1-bfd-session-s3]commit

===========

配置文件

<s3>dis cu

#

bfd

#

bfd s1 bind peer-ip default-ip interface GigabitEthernet0/0/1

 discriminator local 31

 discriminator remote 13

 commit

#

bfd s2 bind peer-ip default-ip interface GigabitEthernet0/0/2

 discriminator local 32

 discriminator remote 23

 commit

#

return

<s3>

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

<s2>dis cu

#

bfd

#

interface NULL0

#

bfd s1 bind peer-ip default-ip interface GigabitEthernet0/0/1

 discriminator local 21

 discriminator remote 12

 commit

#

bfd s3 bind peer-ip default-ip interface GigabitEthernet0/0/2

 discriminator local 23

 discriminator remote 32

 commit

#

return

<s2>

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

<s1>dis cu

#

sysname s1

#

bfd

#

bfd s2 bind peer-ip default-ip interface GigabitEthernet0/0/1

 discriminator local 12

 discriminator remote 21

 commit

#

bfd s3 bind peer-ip default-ip interface GigabitEthernet0/0/2

 discriminator local 13

 discriminator remote 31

 commit

#

return

<s1>

=========

查看BFD 状态

<s1>dis bfd session all

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

Local Remote     PeerIpAddr      State     Type        InterfaceName           

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

12    21         224.0.0.184     Up        S_IP_IF     GigabitEthernet0/0/1    

13    31         224.0.0.184     Up        S_IP_IF     GigabitEthernet0/0/2    

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

     Total UP/DOWN Session Number : 2/0

<s1>

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

<s1>dis bfd session all verbose

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

Session MIndex : 256       (One Hop) State : Up        Name : s2            

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

  Local Discriminator    : 12               Remote Discriminator   : 21       

  Session Detect Mode    : Asynchronous Mode Without Echo Function            

  BFD Bind Type          : Interface(GigabitEthernet0/0/1)                    

  Bind Session Type      : Static   

  Bind Peer IP Address   : 224.0.0.184                                        

  NextHop Ip Address     : 224.0.0.184                                        

  Bind Interface         : GigabitEthernet0/0/1                               

  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                    : 255      

  Proc Interface Status  : Disable  

  WTR Interval (ms)      : -        

  Active Multi           : 3        

  Last Local Diagnostic  : Control Detection Time Expired                      

  Bind Application       : No Application Bind

  Session TX TmrID       : 1043             Session Detect TmrID   : 1044     

  Session Init TmrID     : -                Session WTR TmrID      : -        

  Session Echo Tx TmrID  : -         

  PDT Index              : FSM-0 | RCV-0 | IF-0 | TOKEN-0                     

  Session Description    : -        

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

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

Session MIndex : 257       (One Hop) State : Up        Name : s3            

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

  Local Discriminator    : 13               Remote Discriminator   : 31       

  Session Detect Mode    : Asynchronous Mode Without Echo Function            

  BFD Bind Type          : Interface(GigabitEthernet0/0/2)                    

  Bind Session Type      : Static   

  Bind Peer IP Address   : 224.0.0.184                                         

  NextHop Ip Address     : 224.0.0.184                                        

  Bind Interface         : GigabitEthernet0/0/2                               

  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                    : 255      

  Proc Interface Status  : Disable  

  WTR Interval (ms)      : -        

  Active Multi           : 3        

  Last Local Diagnostic  : Control Detection Time Expired                     

  Bind Application       : No Application Bind

  Session TX TmrID       : 1049             Session Detect TmrID   : 1050     

  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 : 2/0

<s1>

 

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