Example for Enabling BFD to Modify the PST

This section provides an example for enabling BFD to modify the PST. After the configuration is complete, an upper-layer protocol switches traffic to a backup link if a link fault occurs.

Networking Requirements

If BFD is enabled to modify the PST, BFD can modify the PST after detecting that an interface goes Down. This function allows the lower layer to detect the fault based on the PST change.

LDP FRR and IP FRR obtain a BFD detection result based on a PST change.

On the network shown in Figure 1, a BFD session in asynchronous mode is set up to detect faults in the link between Device A and Device B.

Figure 1 Enabling BFD to modify the PST

Interfaces 1 in this example are GE 0/1/0.

Precautions

BFD sessions must be established on both ends.

Configuration Roadmap

The configuration roadmap is as follows:

Enable BFD globally on Device A and Device B.
Create single-hop BFD sessions and bind them to the outbound interfaces on Device A and Device B, respectively.
Enable BFD to modify the PST.

Data Preparation

To complete the configuration, you need the following data:

Peer IP address monitored by BFD
Local and remote discriminators of BFD sessions
BFD session names

Procedure

Assign IP addresses to the interfaces connecting Device A and Device B.

# Configure Device A.

<HUAWEI> system-view
[~HUAWEI] sysname DeviceA
[*HUAWEI] commit
[~DeviceA] interface gigabitethernet 0/1/0
[~DeviceA-GigabitEthernet0/1/0] undo shutdown
[*DeviceA-GigabitEthernet0/1/0] ip address 10.1.1.1 24
[*DeviceA-GigabitEthernet0/1/0] commit
[~DeviceA-GigabitEthernet0/1/0] quit
[~DeviceA] quit

# Configure Device B.

<HUAWEI> system-view
[~HUAWEI] sysname DeviceB
[*HUAWEI] commit
[~DeviceB] interface gigabitethernet 0/1/0
[~DeviceB-GigabitEthernet0/1/0] undo shutdown
[*DeviceB-GigabitEthernet0/1/0] ip address 10.1.1.2 24
[*DeviceB-GigabitEthernet0/1/0] commit
[~DeviceB-GigabitEthernet0/1/0] quit
[~DeviceB] quit

After the configuration is complete, Device A and Device B can ping each other. The following example uses the command output on Device A.

<DeviceA> ping 10.1.1.2
PING 10.1.1.2 : 56  data bytes, press CTRL_C to break
    Reply from 10.1.1.2: bytes=56 Sequence=1 ttl=255 time=3 ms
    Reply from 10.1.1.2: bytes=56 Sequence=2 ttl=255 time=1 ms
    Reply from 10.1.1.2: bytes=56 Sequence=3 ttl=255 time=1 ms
    Reply from 10.1.1.2: bytes=56 Sequence=4 ttl=255 time=1 ms
    Reply from 10.1.1.2: bytes=56 Sequence=5 ttl=255 time=1 ms

  --- 10.1.1.2 ping statistics ---
    5 packet(s) transmitted
    5 packet(s) received
    0.00% packet loss
    round-trip min/avg/max = 1/1/3 ms

Configure single-hop BFD.

# Configure Device A.

[~DeviceA] bfd
[*DeviceA-bfd] quit
[*DeviceA] bfd pst bind peer-ip 10.1.1.2 interface gigabitethernet 0/1/0
[*DeviceA-bfd-session-pst] discriminator local 1
[*DeviceA-bfd-session-pst] discriminator remote 2
[*DeviceA-bfd-session-pst] commit
[~DeviceA-bfd-session-pst] quit

# Configure Device B.

[~DeviceB] bfd
[*DeviceB-bfd] quit
[*DeviceB] bfd pst bind peer-ip 10.1.1.1 interface gigabitethernet 0/1/0
[*DeviceB-bfd-session-pst] discriminator local 2
[*DeviceB-bfd-session-pst] discriminator remote 1
[*DeviceB-bfd-session-pst] commit
[~DeviceB-bfd-session-pst] quit

After completing the configurations, run the display bfd session all verbose command on Device A or Device B. The command output shows that a single-hop BFD session has been established and its status is Up. The following example uses the command output on Device B.

[~DeviceB] display bfd session all verbose
(w): State in WTR  (*): State is invalid
------------------------------------------------------------------------------
  (One Hop)   State : Up                    Name : pst
------------------------------------------------------------------------------
  Local Discriminator    : 2                Remote Discriminator   : 1
  Session Detect Mode    : Asynchronous Mode Without Echo Function
  BFD Bind Type          : Interface(GigabitEthernet0/1/0)
  Bind Session Type      : Static
  Bind Peer IP Address   : 10.1.1.1
  Bind Interface         : GigabitEthernet0/1/0
  FSM Board Id           : 1                TOS-EXP                : 7
  Min Tx Interval (ms)   : 10               Min Rx Interval (ms)   : 10
  Actual Tx Interval (ms): 10               Actual Rx Interval (ms): 10
  Local Detect Multi     : 3                Detect Interval (ms)   : 30
  Echo Passive           : Disable          Acl Number             : -
  Destination Port       : 3784             TTL                    : 255
  Proc Interface Status  : Disable          Process PST            : Disable
  WTR Interval (ms)      : 0                Config PST             : Disable
  Active Multi           : 3
  Last Local Diagnostic  : No Diagnostic
  Bind Application       : No Application Bind
  Session TX TmrID       : 0                Session Detect TmrID   : 0
  Session Init TmrID     : -                Session WTR TmrID      : -
  Session Echo Tx TmrID  : -
  Session Description    : -
------------------------------------------------------------------------------

     Total UP/DOWN Session Number : 1/0

Enable BFD to modify the PST on Device A and Device B.

# Configure Device A.

[~DeviceA] bfd pst
[*DeviceA-bfd-session-pst] process-pst
[*DeviceA-bfd-session-pst] commit
[~DeviceA-bfd-session-pst] quit

# Configure Device B.

[~DeviceB] bfd pst
[*DeviceB-bfd-session-pst] process-pst
[*DeviceB-bfd-session-pst] commit
[~DeviceB-bfd-session-pst] quit

Verify the configuration.

After completing the configurations, run the display bfd session all verbose command on Device A or Device B. The command output shows that Process PST is Enable. The following example uses the command output on Device B.

[~DeviceB] display bfd session all verbose
(w): State in WTR  (*): State is invalid
------------------------------------------------------------------------------
  (One Hop)   State : Up                    Name : pst
------------------------------------------------------------------------------
  Local Discriminator    : 2                Remote Discriminator   : 1
  Session Detect Mode    : Asynchronous Mode Without Echo Function
  BFD Bind Type          : Interface(GigabitEthernet0/1/0)
  Bind Session Type      : Static
  Bind Peer IP Address   : 10.1.1.1
  Bind Interface         : GigabitEthernet0/1/0
  FSM Board Id           : 1                TOS-EXP                : 7
  Min Tx Interval (ms)   : 10               Min Rx Interval (ms)   : 10
  Actual Tx Interval (ms): 10               Actual Rx Interval (ms): 10
  Local Detect Multi     : 3                Detect Interval (ms)   : 30
  Echo Passive           : Disable          Acl Number             : -
  Destination Port       : 3784             TTL                    : 255
  Proc Interface Status  : Disable          Process PST         : Enable
  WTR Interval (ms)      : 0                Local Demand Mode      : Disable
  Active Multi           : 3
  Last Local Diagnostic  : No Diagnostic
  Bind Application       : No Application Bind
  Session TX TmrID       : 0                Session Detect TmrID   : 0
  Session Init TmrID     : -                Session WTR TmrID      : -
  Session Echo Tx TmrID  : -
  Session Description    : -
------------------------------------------------------------------------------

     Total UP/DOWN Session Number : 1/0

Configuration Files

Device A configuration file

#
sysname DeviceA
#
bfd
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.1 255.255.255.0
#
bfd pst bind peer-ip 10.1.1.2 interface GigabitEthernet0/1/0
 discriminator local 1
 discriminator remote 2
 process-pst
return

Device B configuration file

#
sysname DeviceB
#
bfd
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.2 255.255.255.0
#
bfd pst bind peer-ip 10.1.1.1 interface GigabitEthernet0/1/0
 discriminator local 2
 discriminator remote 1
 process-pst
return