Spanning Tree Protocol

STP:

• Root Bridge Election
• Elect one Root Port per bridge
• Elect Designated Ports on Root bridge

Root Bridge Election:

• Based on Bridge ID of Switch
• ID contain:
• Bridge Priority (0-61440, increment of 4094)
• System ID ( VLAN no.)
• MAC Add (become Spanning Tree MAC address)
• Lowest Bridge ID containing Switch become Root Bridge

Manual Selection of Root Bridge:

• spanning-tree vlan [ids] priority         (lowest priority number will become root bridge)
• spanning-tree vlan [ids] root [primary|secondary]
•  without giving any priority value switch become root bridge
• by automatically decrease the priority value than current root bridge

Root bridge verification:

• show spanning-tree root
• show spanning-tree vlan [id]

ADDITIONAL:

it repeatedly looks for the optimal solution, selecting an “optimal” candidate every time.