Dell EMC SmartFabric OS10 User Guide Release 10.5.0

Rapid-PVST assigns the root bridge according to the lowest bridge ID. Primary configuration assigns 24576 as the bridge priority whereas secondary configuration assigns 28672 as the bridge priority.

spanning-tree vlan vlan-id root primary command ensures that the switch has the lowest bridge priority value by setting the predefined value of 24,576. If an alternate root bridge is required, use the spanning-tree vlan vlan-id root secondary command. The command sets the priority for the switch to the predefined value of 28,672. If the primary root bridge fails, the command ensures that the alternate switch becomes the root bridge. It also assumes that the other switches in the network have a defined default priority value of 32,768.

• Configure the device as the root or secondary root in CONFIGURATION mode.

  spanning-tree vlan vlan-id root {primary | secondary}

  • vlan-id — Enter the VLAN ID number, from 1 to 4093.
  • primary — Enter the bridge as primary or root bridge. The primary bridge value is 24576.
  • secondary — Enter the bridge as the secondary root bridge. The secondary bridge value is 28672.

Configure root bridge as primary

OS10(config)# spanning-tree vlan 1 root primary

Verify root bridge information

OS10# show spanning-tree active

Spanning tree enabled protocol rapid-pvst with force-version rstp
VLAN 1
Executing IEEE compatible Spanning Tree Protocol
Root ID    Priority 24577, Address 90b1.1cf4.a523
Root Bridge hello time 2, max age 20, forward delay 15
Bridge ID    Priority 24577, Address 90b1.1cf4.a523
We are the root of VLAN 1
Configured hello time 2, max age 20, forward delay 15
Interface                                                  Designated
Name            PortID   Prio  Cost Sts  Cost Bridge ID           PortID
----------------------------------------------------------------------
ethernet1/1/5   128.276  128   500  FWD  0    24577  90b1.1cf4.a523  128.276
ethernet1/1/6   128.280  128   500  LRN  0    24577  90b1.1cf4.a523  128.280
Interface
Name            Role PortID  Prio Cost Sts  Cost Link-type Edge
-------------------------------------------------------------
ethernet1/1/5   Desg 128.276 128  500  FWD  0    AUTO      No
ethernet1/1/6   Desg 128.280 128  500  LRN  0    AUTO      No