1 © 2003, cisco systems, inc. all rights reserved. ccna 3 v3.0 module 7 spanning tree protocol
TRANSCRIPT
1© 2003, Cisco Systems, Inc. All rights reserved.
CCNA 3 v3.0 Module 7 Spanning Tree Protocol
444© 2003, Cisco Systems, Inc. All rights reserved.
Objectives
• Redundant topologies
• Spanning Tree Protocol
555© 2003, Cisco Systems, Inc. All rights reserved.
Redundant topologies
666© 2003, Cisco Systems, Inc. All rights reserved.
Redundancy
Redundant networking topologies are designed to ensure that networks continue to function in the presence of single points of failure.
777© 2003, Cisco Systems, Inc. All rights reserved.
Redundant Topologies
• A goal of redundant topologies is to eliminate network outages caused by a single point of failure.
• All networks need redundancy for enhanced reliability.
888© 2003, Cisco Systems, Inc. All rights reserved.
Simple Redundant Switched Topology
999© 2003, Cisco Systems, Inc. All rights reserved.
Broadcast Storm
101010© 2003, Cisco Systems, Inc. All rights reserved.
Multiple Frame Transmissions
111111© 2003, Cisco Systems, Inc. All rights reserved.
Media Access Control Database Instability
In a redundant switched network, it is possible for switches to learn the wrong information. A switch can learn that a MAC address is on a port when it is not.
121212© 2003, Cisco Systems, Inc. All rights reserved.
Spanning Tree Protocol
131313© 2003, Cisco Systems, Inc. All rights reserved.
Using Bridging Loops for Redundancy
141414© 2003, Cisco Systems, Inc. All rights reserved.
Spanning-Tree Protocol
151515© 2003, Cisco Systems, Inc. All rights reserved.
Spanning Tree Link Costs
161616© 2003, Cisco Systems, Inc. All rights reserved.
A Spanning Tree
171717© 2003, Cisco Systems, Inc. All rights reserved.
Spanning-Tree Operation
• One root bridge per network.
• One root port per nonroot bridge.
• One designated port per segment.
• Nondesignated ports are unused.
181818© 2003, Cisco Systems, Inc. All rights reserved.
Bridge Protocol Data Unit
Bridge protocol data unit (BPDU)
191919© 2003, Cisco Systems, Inc. All rights reserved.
Bridge IDs
202020© 2003, Cisco Systems, Inc. All rights reserved.
Spanning-Tree Port States
212121© 2003, Cisco Systems, Inc. All rights reserved.
Spanning-Tree Recalculation
A switched internetwork has converged when all the switch and bridge ports are in either the forwarding or blocked state.
222222© 2003, Cisco Systems, Inc. All rights reserved.
Rapid Spanning-Tree Protocol
• The standard and protocol introduce the following:
Clarification of port states and roles
Definition of a set of link types that can go to forwarding state rapidly
Allowing switches, in a converged network, to generate their own BPDUs rather than relaying root bridge BPDUs
232323© 2003, Cisco Systems, Inc. All rights reserved.
Rapid Spanning-Tree Port Designations
The Rapid Spanning Tree Protocol, IEEE 802.1w, will eventually replace the Spanning Tree Protocol, IEEE 802.1D.