But there is a protocol called spanningtree protocol stp that is used to stop switching loops in a layer2 switched network. Ccna 200120 chapter 1 spanning tree protocol flashcards. Cisco ccna spanning tree protocol stp spanning tree protocols stps main task is to stop network loops from occurring on your layer2 network bridges or switches. This document descibes spanning tree protocol stp in a wireless environment. Cisco spanning tree protocol guide stp examples and. Just like every coin has two sides, a redundant link, along with several advantages, has some disadvantages. For an ethernet network to function properly, only one active. A redundant link is usually created for backup purposes. This is where an understanding of stp spanning tree protocol comes into play.
Stp is a layer 2 link management protocol that provides path redundancy while preventing loops in the network. Ccna in 21 hours about this book introduction this book gives a basic illustration for ccna cisco certified network associate, 640802 syllabus, which is a prerequisite certificate for most of the cisco certifications. Chapter 6 switching and spanning tree protocol free ccna. This webcast shows you the stp topics for which youre responsible on the ccna rs 200125 or icnd2 200105. In the first chapter, you were introduced to bit of switching and switches. The bridges send configuration bpdus through the ethernet and radio ports. This section describes how spanningtree features work.
The unique bridge id wireless bridge priority and mac address associated with each vlan on each wireless bridge the spanningtree path cost to the spanningtree root the port identifier port priority and mac address associated with each layer 2 interface. Root selection varies depending on the bid of each switch in your lab resulting in varying outputs. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks. Cisco ccna spanning tree basics this is a course that will start from the very beginning of spanning tree and you will walk away with how it begins. Stp blocks some ports on switches with redundant links to prevent broadcast storms and ensure loopfree topology. This content is only accessible by registered users. How is the ttl field used to prevent indefinite looping of ip datagrams. In preparation of your ccna exam, we want to make sure we cover the various concepts that we could see on your cisco ccna exam. To view the information about the stp operation, you can use the show spanning tree command from the privilegedexec mode. Spanning tree protocol stp is enabled, every switch in the network starts in the blocking state and later changes to the listening and learning states. The golden rule of spanningtree protocol is lower is better. Understanding and configuring spanning tree protocol stp.
Stp spanning tree protocol explained with examples. You already know that the layer 2 of the osi model deals with switching frames in the local network and that switches work at this layer. At this time there were no switches yet, only bridges, but. The bpdus communicate and compute the spanningtree topology. Switches running stp will build a map or topology of the entire switching network. So therefore, if there is a tie in our value with spanningtree protocol, there has to be a tiebreaker mechanism. It is desirable to have redundant links in a switched lan so that a single link failure cannot interrupt normal operation of the network. Root selection varies depending on the bid of each switch in your lab. As layer 2 networks grew, it quickly became evident that a system to prevent loops was needed if lans were to continue to function. Before we talk about spanning tree protocol, lets organize the different variants of stp. Spanning tree protocol variants best cisco ccna ccnp and. Stp will identify if there are any loops, and then disable or block. In this exercise, we will explain how does the spanningtree protocol work. Path of packet i count this as a technology topic because it involves the forwarding mechanisms for the various catalyst platforms, spanning tree protocol, multicast, and quality of service.
Stp uses the spanningtree algorithm spa to create a topology database of the nework. Digital equipment corporation created a protocol called spanning tree protocol stp to prevent broadcast storms and network loops at layer 2. Spanning tree protocol stp ensures a loopfree topology in a local area network lan made up of switches. With stp in place, you can have redundant links between switches in order to provide redundancy. To prevent loops, spa places some interfaces into forwarding state and some interfaces into blocking state. Spanning tree protocol stp is a network protocol designed to prevent layer 2 loops. Chapter 6 switching and spanning tree protocol freeccna 20150921t14. In 2008 free ccna workbook originally started as a sharable pdf but quickly evolved into the largest ccna training lab website on the net.
The basic function of stp is to prevent bridge loops and the broadcast radiation that results from them. Thats where we can have a convergence time of 50 seconds and that where even, if we have multiple vlans, all of the vlans are using the same instances of spanning tree protocol, its called a cst or common spanning tree. Start studying ccna 200120 chapter 1 spanning tree protocol. Free cisco ccna tutorial cisco ccna spanning tree basics. Cbt nuggets trainer jeremy cioara explains how to configure spanning tree protocol as well as the different types of spanning tree protocols. Stp spanning tree protocol automatically removes layer 2 switching loops by shutting down the redundant links. For a layer 2 network to function properly, only one active path can exist between any two stations. In 2008 free ccna workbook originally started as a sharable pdf but quickly evolved into. The stable, active spanningtree topology of a network is determined by the following factors. Spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches. The following image shows how the stp changes a physically looped topology into a virtually looped free topology. Spanning tree protocol stp spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. Configure and troubleshoot cisco spanning tree stp learn how to configure stp, portfast and bpduguard on cisco switches free ccna course handson lab networking fundamentals switching troubleshooting written by alessandro maggio.
As you already know, what we have just seen is a loop and such loops can bring a network to a grinding halt. Furthermore, cisco loves to give you really complex topologies like the one we created. One of the topics on the ccna rs version 3 exam is spanning tree protocol stp. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Configuring switchport spanning tree portfast free ccna. Multiple spanning tree multiple spanning tree protocol mstp network organized in regions regions have their own multiple spanning tree instances spanningtree topologies vlans are associated to mstis one common spanning tree cst for the entire network mstp based on rstp rapid stp. Spanning tree protocol understanding spanning tree protocol 3 cisco 3200 series wireless mic software configuration guide when the bridges in a network are powered up, each br idge functions as the stp root. As you prepare for your ccna certification exam, you will be called upon to merge multiple concepts you learned into one exam question. The output of this command can be divided into three subsets. Spanning tree protocol stp cisco ccna certification. You are not allowed to use the spanningtree root command. Vlan0005 spanning tree enabled protocol ieee root id priority 32773 address 00.
Configure and troubleshoot cisco spanning tree stp. On each switch, display the spanning tree table with the show spanningtree command. Make sure switch grasshopper is the root bridge for vlan 40, switch butterfly should be the backup in case switch butterfly fails. Blocking during blocking state, the port is listening to and processing bpdus after 20 seconds, the switch port changes from the blocking state to the listening state. How does stp decides in which state to port will be placed. What is the byte order used for transmitting datagram headers in the tcpip protocol suite. Spanning tree algorithm is used to calculate a loopfree path. With the advent of layer 3 switching in lan environments, bridging now competes. Understanding and configuring spanning tree protocol stp cisco. It vigilantly monitors the network to find all links, making sure that no loops occur by blocking any redundant ones. We block fa02 and so we know now that we could cable two switches together, but spanningtree protocol hits us with a mallet and it says, you know what, you cant have your cake and eat it too, you cant add extra throughput to these two switches. Spanningtree protocol is a link management protocol that provides path redundancy while preventing undesirable loops in the network.
Introduction to stp, spanning tree protocol, broadcast storm, topological loop, switch macaddress table corruption,stp pdf file download, pdf file download, ethernet bridge, ethernet switch,layer 2 topological loop,ieee 802. The original stp was developed by radia perlman while working for dce back in 1990. This will be discussed in lab 415 configuring multiple spanning tree protocol. Ccna course gives you the basic knowledge to operate a computer network. If you have not yet registered, you will be prompted to register, before proceeding to access this content. So to assist you, below we will discuss one of the more difficult ccna concepts. Once the root switch is elected, each of the ports is given a role depending on its place within the stp topology. Stp is a layer 2 link management protocol that provides path redundancy while.
The main purpose of stp is to ensure that you do not create loops when you have redundant paths in your network. The spanning tree protocol was created by dec digital equipment corporation now compaq. Stp is enabled by default on all cisco switches, for all vlans. Change the hello timer on all switches for vlan 10 to 4 seconds. A redundant link is an additional link between two switches. Spanning tree protocol views the physical links in an. This tutorial explains what the stp protocol is and how it removes.
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