STP

Redundant Layer 2 Topologies

Redundancy

Simple network VLAN mangement

Starting point

Path Failure - Access to Distribution

Path Failure - Distribution to Core

Switch Failure - Distribution layer

Switch Failure - Core layer

Issues with Redundancy

Layer 2 Loops

Broadcast loops

Real-world Redundancy Issues

Non-Redundant network topology

Loops from 2 connections in the same switch

Loops from connections to a second switch

Loops int the cubicles

Introduction to STP

The Spanning Tree Algorithm

STP Topology

STP Redundancy

STP Port names

Root ports - Switch ports closest to the root bridge.
Designated ports - All non-root ports that are still permitted to forward traffic on the network.
Non-designated ports - All ports configured to be in a blocking state to prevent loops.

Root Bridge

BID fields

Port cost

Configuring port costs

Path Cost

Verify port and path costs

STP BPDU

BPDU Fields

Version - The version field indicates the version of the protocol, This field contains the value zero.
Message type - The message type field indicated the type of message, this field contains the value zero.
Flags - The flags field includes one of the following: Topology change(TC) bit, which signals a topology change in the event a path to the root bridge has been disrupted. Topology change acknowledgment(TCA) bit, which is set to acknowledge receipt of a configuration messege with the TC bit set.
Root ID - The Root ID field indicates the root bridge by listing its 2-byte prority followed by its 6-byte MAC address ID.
Bridge ID - The Bridge ID field indicates the priority and MAC address ID of the bridge sending the message
Port ID - The Port ID field indicates the port number from which the configuration message was sent.
Forward Delay - The Forward delay field indicates the length of time that bridges should wait before transitioning to a new state after topology change.