S12700 V200R012C00 Configuration Guide - Ethernet Switching

Involved Network Elements

Other network elements also need to support VBST.

Licensing Requirements

VBST is a basic feature of a switch and is not under license control.

Version Requirements

NOTE:

For details about software mappings, visit Hardware Query Tool and search for the desired product model.

Feature Limitations

• Table 16-4 describes the specifications of VBST.

  Table 16-4  Specifications of VBST

  Item	Specification
  Number of protected VLANs	128
  PV number (The PV number is the total number of VLANs into which all VBST-enabled interfaces are added. The VLANs have been established and VBST has been enabled in the VLANs.)	In versions earlier than V200R012, EE series, X series, ET1D2L02QSC0, ET1D2L08QSC0, and ET1D2X48SEC0 cards support a maximum of 1200 PVs, and other cards support a maximum of 300 PVs. In V200R012 and later versions, you can run the display vbst port-vlan statistics command to check the supported PV number. The maximum PV number supported by a switch is the sum of PV quantities supported by cards that are currently installed. For an Eth-Trunk: In V200R009 and earlier versions, switches support a maximum of 300 PVs. In V200R010 and V200R011, switches support a maximum of 1000 PVs. In V200R012 and later versions, you can run the display vbst port-vlan statistics command to check the supported PV number. NOTICE: The CPU usage of VBST is in direct proportion to the PV number. If the number of occupied PVs exceeds the specifications, the CPU usage may be high. As a result, the switch cannot process tasks in a timely manner, protocol calculation is affected, and the switch cannot be managed by the NMS.

• When VBST is enabled on a ring network, VBST immediately starts spanning tree calculation. Parameters such as the switch priority and port priority affect spanning tree calculation, and change of these parameters may cause network flapping. To ensure fast and stable spanning tree calculation, perform basic configurations on the switch and interfaces before enabling VBST.

• If the protected instance has been configured in a SEP segment or ERPS ring but the mapping between protected instances and VLANs is not configured, VBST cannot be enabled.

• VBST cannot be enabled in the ignored VLAN or control VLAN used by ERPS, RRPP, SEP, or Smart Link.

• If VLAN mapping or VLAN stacking is configured on an interface corresponding to the VLAN, VBST negotiation for this VLAN will fail.

• If 1:N (N>1) mapping between MSTIs and VLANs has been configured on the switch, delete the mapping before changing the STP working mode to VBST.
• If the stp vpls-subinterface enable command has been configured on a switch, run the undo stp vpls-subinterface enable command on an interface before changing the STP working mode to VBST.

• If the device has been configured as the root bridge or secondary root bridge, run the undo stp vlan { vlan-id1 [ to vlan-id2 ] } &<1-10> root command to disable the root bridge or secondary root bridge function and run the stp vlan { vlan-id1 [ to vlan-id2 ] } &<1-10> priority priority command to change the device priority.

• When more than 128 MSTIs are dynamically specified, STP is displayed as disabled in a created VLAN in the configuration file, for example, stp vlan 100 disable.

• To prevent frequent network flapping, ensure that the values of Hello time, Forward Delay, and Max Age conform to the following formulas:

  • 2 x (Forward Delay - 1.0 second) ≥ Max Age

  • Max Age ≥ 2 x (Hello Time + 1.0 second)

• It is recommended that fast convergence in normal mode be used. If fast is used, frequently deleting ARP entries may result in 100% CPU usage of the MPU and LPU. As a result, packet processing expires and network flapping occurs.

• After all ports are configured as edge ports and BPDU filter ports in the system view, no ports on the switch send BPDUs or negotiate the VBST status with directly connected ports on the remote device. All ports are in forwarding state. This may cause loops on the network, leading to broadcast storms. Exercise caution when you configure a port as an edge port and BPDU filter port.

• After a port is configured as an edge port and BPDU filter port in the interface view, the port does not process or send BPDUs. The port cannot negotiate the VBST status with the directly connected port on the peer device. Exercise caution when you configure a port as an edge port and BPDU filter port.

• Root protection takes effect only on designated ports.

• If a switch has an alternate port (backup of the root port), configure loop protection on both the root port and alternate port.