Bridge Id, Switch Priority, And Extended System Id - Cisco 3032 Software Configuration Manual

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Understanding Spanning-Tree Features

StackWise Plus

RP = root port

DP = designated port

BP = blocked port

All paths that are not needed to reach the root switch from anywhere in the switched network are placed

in the spanning-tree blocking mode.

Bridge ID, Switch Priority, and Extended System ID

The IEEE 802.1D standard requires that each switch has an unique bridge identifier (bridge ID), which

controls the selection of the root switch. Because each VLAN is considered as a different logical bridge

with PVST+ and rapid PVST+, the same switch must have a different bridge IDs for each configured

VLAN. Each VLAN on the switch has a unique 8-byte bridge ID. The 2 most-significant bytes are used

for the switch priority, and the remaining 6 bytes are derived from the switch MAC address.

Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide

Only one outgoing port on the stack root switch is selected as the root port. The remaining switches

in the stack become its designated switches (Switch 2 and Switch 3) as shown in

The shortest distance to the root switch is calculated for each switch based on the path cost.

A designated switch for each LAN segment is selected. The designated switch incurs the lowest path

cost when forwarding packets from that LAN to the root switch. The port through which the

designated switch is attached to the LAN is called the designated port.

Spanning-Tree Port States in a Switch Stack

Blade switch stack

Configuring STP

Spanning-tree root

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