Root selection varies depending on the bid of each switch in your lab resulting in varying outputs. Spanningtree protocol stp is a layer 2 protocol that utilizes a specialpurpose algorithm to discover physical loops in a network and effect a logical loopfree topology. 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 documents main purpose is to explain the logic behind the functioning of spanning tree protocol. Understanding spanning tree protocol this section describes how spanningtree features work. This document is freely given, and can be freely distributed. The spanning tree protocol was developed by dec and was revised in the ieee 802. I will be concentrating on the main topics covered in the ccna icnd 2 exam. This is the first in a series of posts on spanning tree, in this post i will be describing the need for spanning tree protocol stp in modern lan environments. This document descibes spanning tree protocol stp in a wireless environment. How to configure spanning tree loop guard ccna ask itmen. Modify spanning tree to achieve load balancing modify the spanning tree configuration so that all six trunks are in use.
Fundamentals of stp spanning tree protocol part i the logic. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks. Spanning tree protocol overview the plugandplay spanning tree protocol stp, a layer 2 protocol that ensures a loopfree topology in bridged lans, has been around for decades. At this time there were no switches yet, only bridges, but because bridges and switches technically do the same job only switches do it more efficiently and have more features they suffer from. The spanning tree protocol prevents looping traffic in a redundant switched network by blocking traffic on the redundant links. The spanning tree feature cannot be turned off in switches on a perport basis. 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. Unless you change this value, a switch that has the lowest mac address. Rapid spanning tree protocol rstp is another name for the 802. Select the ports tab to configure the ports associated with this spanning tree. On each switch, display the spanning tree table with the show spanningtree command. Root selection varies depending on the bid of each switch in your lab. By default a cisco switch use pvst per vlan spanning tree but if we use the command show spanning tree with the default configuration the output is.
Just like every coin has two sides, a redundant link, along with several advantages, has some disadvantages. Rapid spanning tree protocol rstp one big disadvantage of stp is the low convergence which is very important in switched network. I have attached the complete document in pdf format at the end, for download. This document explains the spanning tree protocol stp root guard feature. The spanning tree protocol stp is designed to prevent layer 2 loops. On each bridge, select a root port port with the least cost path to the root bridge. Nov 16, 2016 one of the topics on the ccna rs version 3 exam is spanning tree protocol stp. In 2008 free ccna workbook originally started as a sharable pdf but quickly evolved into the largest ccna training. However, the contents of this document cannot be altered, without my written consent. Spanning tree enabled switches exchange spanning tree protocol messages bpdu to form a loopfree topology.
Thanks must go out to rick graziani of cabrillo college. Second, when redundant loops are planned on a network, stp deals with remediation of network. In a bridge or switch topology for purposes of stp, bridges and switches are identical in operation, it is desirable to physically cable redundant paths to provide fault tolerance. At this time there were no switches yet, only bridges, but because bridges and switches technically. Stp configuration lab1 open the packet tracer scenario. The collective set of forwarding ports creates a single path over which frames are sent between ethernet segments. Stp is a layer 2 link management protocol that provides path redundancy while preventing loops in the network. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Intended audience this document is an implementation guide for deploying the recently ratified 802. There are no specific requirements for this document. On each switch, display the spanning tree table with the show spanning tree command. Stp can be considered to be converged after what three steps have taken place.
Spanning tree protocol this document descibes spanning tree protocol stp in a wireless environment. Spanning tree protocol stp is a layer 2 protocol that utilizes a specialpurpose algorithm to discover physical loops in a network and effect a logical loopfree topology. Stp will identify if there are any loops, and then disable or block. Ccna training rapid spanning tree protocol rstp tutorial. Spanning tree protocol stp was developed before switches were created in order to deal with an issue that occurred with networks that were implementing network bridges.
Spanning tree protocol in layer 2layer 3 environments. Spanning tree protocol ccnax 200120 ccna practice tests. Detailed explanations of the basic functionality of each spanning tree protocol is outside the scope of this document. This lab will discuss and demonstrate the configuration and verification of 802. This document presents an overview of rapid spanning tree protocol rstp and multiple spanning tree protocol mstp and how to implement each. The root bridge on a lan is selected by an election. Configuring multiple spanning tree protocol mstp free. The basic function of stp is to prevent bridge loops and the broadcast radiation that results from them. Networks should be designed to reconverge rapidly so that a fault is bypassed fault tolerance is achieved by redundancy. Spanning tree protocol stp spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. Before proceeding, save as stp configuration lab1working. Spanning tree protocol stp is another name for the 802. First, it prevents problems caused by loops on a network. The node with the smallest id is selected the root bridge 2.
Configuring pervlan spanning tree protocol free ccna. Rapid spanning tree protocol rstprstp is defined in ieee 802. Introduction to spanning tree spanning tree is a protocol that runs on our switches that helps us to solve loops. This webcast shows you the stp topics for which youre responsible on the ccna rs 200125 or icnd2 200105. To overcome this problem, in 2001, the ieee with document 802. A redundant link is usually created for backup purposes. Stp overview stp is a layer 2 link management protocol that prov ides path redundancy while preventing loops in the network.
In a converged network, ports are either in forwarding or blocking state. For a layer 2 network to function properly, only one active path can exist between any two stations. Observe and explain the default behavior of spanning tree protocol stp, 802. 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. Ccna lab manual router infotech, confidential document only for internal circulation page 2 lab. Ccna security lab securing layer 2 switches topology. Ccna 200120 chapter 2 spanning tree protocol implementation. This documentation is based primarily on the common stp. Mst is commonly used in extremely large networks where running pvst would tax switch resources. Spanningtree protocol stp premium ccna exam questions. All other switches on the network choose a best loop free path to reach the root.
This section describes how spanningtree features work. Based on the exchanged bpdu information, the spanning tree algorithm selects one of the switches on the network as the root switch for the tree topology. Multi spanning tree protocol allows for resource conservation by now requring an instance for every single vlan in the layer 2 network. The biggest issue with stp is that some hardware failures can cause it to fail. Before we talk about spanning tree protocol, lets organize the different variants of stp. Spanning tree protocol assigns a root bridge, root ports for nonroot bridges, and designated port segments. Multiple spanning tree protocol gives you the ability to configure a hierarchical spanning tree topology where you have a common spanning tree instance known as the cist, technically instance 0 in mst configuration mode. This lesson is an introduction to spanning tree, you will learn why we need it, how it works and how you can check the spanning tree topology on your cisco switches. By default, the bridge priority value is set to 32768 in all cisco switches. Switches running stp will build a map or topology of the entire switching network.
Spanning tree enabled switches go through a root election process based on bridge p rotocol data unit. All the ports in forwarding state are considered to be in the current spanning tree. The first spanning tree protocol was invented in 1985 at the digital equipment corporation by radia perlman. Understanding and configuring spanning tree protocol stp. Components used although this document uses cisco catalyst 55005000 switches, the spanning tree principles that the document presents are applicable to almost all devices that support stp. Each switch running stp passes information in a format known as bridge protocol data units. You can use your network topology drawing to document the initial state of all trunk ports. These presentations are the result of a collaboration among the instructors at st. Root selection varies depending on the default bid of each switch.
Rapid spanning tree protocol rstp, which significantly reduces the convergence time after a. When you are adding a spanning tree, select a protocol name. Stp creates a loopfree tree structure consisting of leaves and branches that span the entire layer 2 network. The spanning tree algorithm places each bridgeswitch port in either a forwarding state or a blocking state. Pvst, rapid spanning tree protocolrstp and multi spanning tree protocol mstp. The router commands and output in this lab are from a cisco 1941 router using cisco ios software. Vlan0005 spanning tree enabled protocol ieee root id priority 32773 address 00. This feature is one of the stp enhancements that cisco created. It also includes the contents as well as explanation for certain sections of the bpdu. Spanning tree protocol stp in packet tracer part 1. Stp spanning tree protocol explained with examples.
Rstp keeps the same bpdu format as the original ieee 802. The bridge id is made up of the mac address and priority. Something along the lines of a network diagram with the required info available to mark a port as root, designated, blocking etc. Start studying ccna 200120 chapter 2 spanning tree protocol implementation. Make sure that the routers and switches have been erased and have no startup configurations.
Spanning treeenabled switches go through a root election process based on bridge p rotocol data unit. Jan 31, 2016 hi guys, this post got awarded best publication at the cisco support community. Nor can this document be sold or published without my expressed consent. Spanning tree protocol stp with juniper networks ex series ethernet switches. Understanding and configuring spanning tree protocol stp on. A redundant link is an additional link between two switches. Spanning tree protocol root guard enhancement cisco. This document is targeted at ses and other technical audiences as an. Spanning tree protocol operation is transparent to end stations. Configuring the spanning tree protocol j web procedure. Prerequisites requirements there are no specific requirements for this. Fundamentals of stp spanning tree protocol part i the. It vigilantly monitors the network to find all links, making sure that no loops occur by blocking any redundant ones. Spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches.
Spanning tree also allows a network design to include backup links providing fault tolerance if an active link fails as the name suggests, stp creates a spanning tree that. This exam tests a candidates knowledge and skills related to network fundamentals, network access, ip connectivity, ip services, security fundamentals, and automation and programmability. Stp spanning tree protocol automatically removes layer 2 switching loops by shutting down the redundant links. Understanding spanning tree protocol this section describes how spanning tree features work. This failure creates forwarding loops or stp loops. Stp is enabled by default on all cisco switches, for all vlans.
Configuring pervlan spanning tree protocol free ccna workbook. The spanning tree protocol prevents loops in a redundant network. How to configure spanning tree loop guard, spanning tree protocol stp resolves physically redundant topologies into loopfree, tree like topologies. The main purpose of stp is to ensure that you do not create loops when you have redundant paths in your network. In 1990, the ieee published the first standard for the protocol as 802. Spanning tree protocol stp for ccna rs 200125 and icnd2. Spanning tree protocol interoperability with cisco arista networks. The original stp was developed by radia perlman while working for dce back in 1990. Spanning tree protocol introduction 11012015 jonathan leave a comment this is the first in a series of posts on spanning tree, in this post i will be describing the need for spanning tree protocol stp in modern lan environments.
1185 163 697 1060 353 1127 127 454 1484 29 1181 1341 1450 1263 313 432 1288 273 593 502 1220 145 1467 1076 1287 837 1115 958 1236 448 587 1365