Editing Cisco Commands (section)

=== Set the Root Bridge ===
The root bridge is the central switch in the spanning tree topology. It is chosen based on the lowest bridge priority. A lower priority value increases the likelihood of a switch becoming the root bridge.

Set priority to influence root bridge selection:
* The default priority value is **32768** for all switches.
* Priority is set in increments of **4096**, and this value is added to the VLAN ID (e.g., for VLAN 1, the default bridge priority would be 32768).

To influence the root bridge selection, change the priority value:
 interface GigabitEthernet0/1
  spanning-tree vlan 1 priority 4096
  (Sets a lower priority value, increasing the likelihood of this switch becoming the root bridge for VLAN 1)

Set the root bridge for a specific VLAN:
* To make the current switch the root bridge:
 spanning-tree vlan 1 root primary
  (This automatically sets the priority lower than the default value, typically to 24576, to ensure this switch becomes the root bridge)

* To make the current switch the backup root bridge:
 spanning-tree vlan 1 root secondary
  (This sets the priority higher than the primary root, typically to 28672, making it the backup root bridge)

Alternatively, manually set the root bridge priority:
 interface GigabitEthernet0/1
  spanning-tree vlan 1 priority 24576
  (Sets this switch with a higher priority, making it more likely to become the root bridge)