Enabling Manual LBDT

Context

LBDT needs to send a large number of LBDT packets to detect loops, occupying system resources. Therefore, disable LBDT if loops do not need to be detected.
The blocked ports of LBDT cannot block GVRP packets. To ensure that GVRP runs normally and prevent GVRP loops, do not enable GVRP on the blocked port of LBDT.

An LBDT-enabled interface periodically sends untagged LBDT packets with the destination MAC address as the BPDU MAC address to detect loops. Generally, the switch does not allow BPDUs to pass through, so LBDT can only detect loopbacks on an Interface, but cannot detect a loop on the downstream network or device or between two device interfaces.

To enable LBDT to detect a loop on the downstream network or device, configure LBDT in a specified VLAN. When the connected interface is an access interface or the PVIDs of the inbound and outbound interfaces are the same, you can also run the loopback-detect untagged mac-address command to detect loops.

To enable LBDT to detect a loop between two device interfaces, configure LBDT in a specified VLAN.

On the switch, you can enable LBDT on all interfaces in the system view or on an interface.

Procedure

Run system-view
The system view is displayed.
Run the following commands as required.
- Enable LBDT on all interfaces.
  
  Run the loopback-detect enable command to enable LBDT on all interfaces.
  
  When LBDT needs to be configured on most interfaces, perform this operation. This operation simplifies the configuration.
- Enable LBDT on an interface.
  1. Run the interface interface-type interface-number command to enter the interface view.
  2. Run the loopback-detect enable command to enable LBDT on the interface.
By default, LBDT is disabled on an interface.
Run the following commands as required.
If LBDT Detecting Loopbacks on an Interface is required, skip this step.

If Detecting a Loop on the Downstream Network or Device or Detecting a Loop Between Two Device Interfaces is required, perform this step.
- Configuring LBDT in a specified VLAN
  1. Run interface interface-type interface-number
    
    The interface view is displayed.
  2. Select either of the following configurations to add the VLAN where loops need to be detected.
    - Access interface
      1. Run port link-type access
        
        The link type of the interface is configured as access.
      2. Run port default vlan vlan-id
        
        The access interface is added to the VLAN where loops need to be detected.
    - Hybrid interface
      1. Run port link-type hybrid
        
        The link type of the interface is configured as hybrid.
      2. Run port hybrid tagged vlan { { vlan-id1 [ to vlan-id2 ] }&<1-10> | all } or port hybrid untagged vlan { { vlan-id1 [ to vlan-id2 ] }&<1-10> | all }
        
        The hybrid interface is added to the VLAN where loops need to be detected.
    - Trunk interface
      1. Run port link-type trunk
        
        The link type of the interface is configured as trunk.
      2. Run port trunk allow-pass vlan { { vlan-id1 [ to vlan-id2 ] }&<1-10> | all }
        
        The trunk interface is added to the VLAN where loops need to be detected.
  3. Run loopback-detect packet vlan { vlan-id1 [ to vlan-id2 ] } &<1-8>
    
    Configure LBDT in a specified VLAN.
    
    By default, LBDT is disabled in a VLAN.
  - The specified VLAN must have been created.
  - An interface sends tagged LBDT packets only when the specified VLAN has been created.
  - When the PVID of the interface in the loop is the detected VLAN ID or the interface joins the detected VLAN in untagged mode, VLAN tags of LBDT packets are removed. As a result, the packet priority changes and the system may fail to detect loops.
- Configuring the destination MAC address of untagged LBDT packets
  
  Run the loopback-detect untagged mac-address mac-address command to set the destination MAC address of untagged LBDT packets.
  
  By default, the destination MAC address of untagged LBDT packets is 0180-C200-000A.
  
  Do not configure the destination MAC address of untagged LBDT packets as the destination MAC address of other protocols. You are advised to set the destination MAC address of untagged LBDT packets to a broadcast MAC address (all Fs).