(Optional) Configuring BFD for VPLS PW

After a PW is configured for a VPLS using LDP as signaling, BFD can be configured to monitor the primary PW so that traffic can be immediately switched to the secondary PW in case of a primary PW fault.

Usage Scenario

On a VPLS LDP network, you can configure BFD to detect PW faults, which quickens link fault detection and enhances application-layer service protection.

Currently, static BFD and dynamic BFD are supported. You can choose one according to the network plan.

Pre-configuration Tasks

Before you configure BFD to monitor a VPLS PW, complete the following tasks:

Configure network-layer parameters for devices to communicate.
Configure a PW.
If a remote peer cannot identify the BFD CV Type field value 0x08 used for VCCV, run the mpls l2vpn vccv bfd-cv-negotiation command to change the BFD CV Type field value carried in a Label Mapping packet to be consistent with the remote peer's.

The control word mode of static BFD for VPLS PW does not support the 0x10 or 0x20 type of BFD CV. If the PW-negotiated CV values on both ends are 0x10 or 0x20, a BFD session cannot go Up after negotiation.
If dynamic BFD for VPLS is configured and the BFD CV Type field is negotiated to be 0x10 or 0x20 for the peers, the MTU value of the interface through which BFD control packets are transmitted cannot be less than the BFD control packet length. A BFD control packet's payload is in one of the following lengths:
- Non-authentication: 24 bytes
- MD5 authentication: 48 bytes(For the sake of security, using the HMAC-SHA256 algorithm rather than the MD5 algorithm is recommended.)
- SHA1 authentication: 52 bytes

Procedure

Configure a static BFD session.
1. Run system-view
  The system view is displayed.
2. Run bfd
  BFD is enabled globally, and the global BFD view is displayed.
3. Run quit
  The system view is displayed.
4. Run bfd session-name bind pw vsi vsi-name peer peer-address [ vc-id vc-id ] [ remote-peer remote-peer-address pw-ttl { auto-calculate | ttl-number } ]
  BFD configuration items are created.
5. Run the following commands to configure BFD session discriminators:
  - To configure the local discriminator, run the discriminator local discr-value command.
  - To configure the remote discriminator, run the discriminator remote discr-value command.
  The local BFD session discriminator on one end must be the remote BFD session discriminator on the other end.
6. Run commit
  The configuration is committed.
  
  If the status of a service PW is Down, the BFD session can be established but cannot go Up.
  - BFD for PW must be configured or cancelled on both PEs of a PW. If this function is configured or cancelled only on one end, the PW status between both ends will be inconsistent.
  - To modify the parameters of an existing BFD session, run the min-tx-interval, min-rx-interval, and detect-multiplier commands.
Configure a dynamic BFD session.
1. Run system-view
  The system view is displayed.
2. Run bfd
  BFD is enabled globally, and the global BFD view is displayed.
3. Run quit
  The system view is displayed.
4. Trigger the establishment of a dynamic BFD session.
  1. Run vsi vsi-name
    The VSI view is displayed.
  2. Run pwsignal ldp
    The VSI LDP view is displayed.
  3. Run vsi-id vsi-id
    The VSI ID is configured.
  4. Run peer peer-address
    The VSI peer is configured.
  5. Run peer peer-address pw pw-name
    A VSI LDP PW profile is configured.
  6. Run control-word enable
    The control word function is configured for a VSI.
  7. Run bfd-detect [ detect-multiplier multiplier | min-rx-interval rx-interval | min-tx-interval tx-interval | option-tlv ] ^*
    A dynamic BFD session is configured for the VPLS PW.
    
    The parameters are described as follows:
    detect-multiplier multiplier indicates the BFD detection multiplier.
    
    min-rx-interval rx-interval indicates the Required Min Rx Interval (RMRI), which is the supported minimum interval at which the local device receives BFD control packets.
    
    min-tx-interval tx-interval indicates the Desired Min Tx Interval (DMTI), which is the desired minimum interval at which the local device sends BFD control packets.
    
    The BFD detection parameters actually used may be different from the ones configured:
    Actual local detection interval = Actual interval at which the local device receives BFD control packets x Configured remote BFD detection multiplier
    
    Actual interval at which the local device receives BFD control packets = Max { Configured remote DMTI, Configured local RMRI }
    
    Actual interval at which the local device transmits BFD control packets = Max { Configured local DMTI, Configured remote RMRI }
  8. Run quit
    Return to the system view.
5. Run commit
  The configuration is committed.

Verifying the Configuration

After configuring BFD for VPLS PW, check the configurations.

Run the display bfd session command to check BFD session configurations.