The election decides which switch will become the root bridge, as well as the. Spanning tree protocol through softwaredefined networking tutorial fabiobentostpmininetryu tutorial. Stp, otherwise known as the spanning tree protocol 802. In spanning tree protocol configuration, the shortest path to the root bridge switch is called the root port. Loops are created when multiple paths exist between two.
Stp spanning tree protocol automatically removes layer 2 switching loops by shutting down the redundant links. The main purpose of stp is to ensure that you do not create loops when you have redundant paths in your network. The golden rule of spanningtree protocol is lower is better. Ccna training spanning tree protocol stp tutorial 9tut. By definition a tree is loop free stp does its work at layer 2 datalink of the osi model.
Stp spanning tree protocol explained with examples. The spanning tree protocol stp is a network protocol that ensures a loopfree topology for any bridged ethernet local area network. On each switch, display the spanning tree table with the show spanning tree command. Many people struggle with stp so in this video, we try to break it down as much. What is spanning tree protocol stp sysnettech solutions. As layer 2 networks grew, it quickly became evident that a system to prevent loops was needed if lans were to continue to function. Cisco developed, implemented and published the per vlan spanning tree pvst proprietary protocol using its own proprietary inter switch. Before reading this article you should understand how stp works. Kruskals algorithm follows greedy approach as in each iteration it finds an edge which has least weight and add it to the growing spanning tree. So therefore, if there is a tie in our value with spanningtree protocol, there has to be a tiebreaker mechanism.
The spanning tree portfast is introduced to avoid the network connectivity issues. Thats to say it runs at the ethernet layer and is totally unrelated to dynamic ipbased routing protocols like rip, ospf or olsr which can take into account. The spanning tree algorithm itself is defined by the ieee standard 802. This tutorial explains what the stp protocol is and how it removes loops from the network. Root selection varies depending on the bid of each switch in your lab. For an ethernet network to function properly, only one active. Spanning tree protocol stp is a big topic on the ccna exam. Spanning tree protocol uses a clever mechanism or algorithms. Spanning tree also allows a network design to include spare redundant links to provide automatic backup paths if an active link fails. Root selection varies depending on the bid of each switch in your lab resulting in varying outputs.
Supermicro l2l3 switches configuration guide 5 spanning tree enabled switches exchange spanning tree protocol messages bpdu to form a loopfree topology. Spanning tree root port is used to select path cost. Infrastructure devices such as wireless bridges and switches send and receive spanningtree frames, called bridge protocol data units bpdus, at regular. Spanning tree protocol stp spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. You will learn how spanning tree works and how you can verify the spanning tree config on cisco switches. Trill combines techniques from bridging and routing and is the application of link state routing to the vlanaware customerbridging problem. The different terms in the stp model are explained here. The problem is that when we create redundancyat a layer 2 level of our networks,we create loops that traffic will traverse indefinitely. As the name suggests, it creates a spanning tree within a mesh network of connected layer2 bridges typically ethernet switches, and disables those links that are not part of the spanning tree, leaving a. Download pdf 1,901k view the full article as a pdf this document characterizes and provides some insight into the network traffic behavior when different flavors of spanning tree and device redundancy configurations are deployed between a cisco environment and a dell switching environment. 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.
However, the most common you will encounter will be loops. Dell networking and cisco spanningtree interoperability. 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. Introduction to spanning tree protocol by george thomas, contemporary controls introduction in an industrial automation application that relies heavily on the health of the ethernet network that attaches all the controllers and computers together, a concern exists about what would happen if the network fails. Switches running stp will build a map or topology of the entire switching network. Stp is used by switches to prevent loops occurring on a network, this process is implemented by using spanning tree algorithm in disabling unwanted links and blocking ports that could cause loop.
Learn stp features and functions in detail with examples. Spanning tree protocol, or stp, prevents switching loops in the layer 2 portion of our network. The spanning tree protocol is a link management protocol that is designed to support redundant links while at the same time preventing switching loops in the network. Multiple spanning tree multiple spanning tree protocol mstp network organized in regions regions have their own multiple spanning tree instances spanning tree topologies vlans are associated to mstis one common spanning tree cst for the entire network. Understanding and configuring spanning tree protocol stp. It is quite useful and should be enabled on the switch interfaces. There are the following types of spanning tree protocol 1. Spanningtree protocol is a link management protocol that provides path redundancy while preventing undesirable loops in the network. Introduction to spanning tree protocol stp in bigger networks, having a redundant design is crucial.
Therefore, the switch2 and switch3 ethernet0 0 interfaces above will be configured as root ports. Spanning tree protocol explained step by step youtube. Kruskals algorithm builds the spanning tree by adding edges one by one into a growing spanning tree. The basic function of stp is to prevent bridge loops and ensuing broadcast radiation. Spanning tree is basically used to find a minimum path to connect all nodes in a graph. Spanning tree protocol stp determines the least cost path from the root bridge to other nodes in the networks. This article explain the spanning tree protocol stp. Loops and duplicate frames can have severe consequences on a network.
Spanning tree protocol stp is used to make a loop free network by monitoring the network to track all the links and shut down the least redundant ones. So if you are not sure about stp, please read my article about spanning tree protocol tutorial first. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology in, the ieee introduced rapid spanning tree protocol rstp as w. There are two famous algorithms for finding the minimum spanning tree. Spanning tree protocol in layer 2layer 3 environments. Root bridge is a switch in a single vlan or whole topology according to the type of stp standard used which is responsible for distributing bpdus and block the least redundant port. Redundant network designs allows service continuity in case of link failure. Stp will identify if there are any loops, and then disable or block. Consider, city network as a huge graph and now plans to deploy telephone lines in such a. Spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. Enabling the portfast causes the switch or trunk port to enter the stp forwardingstate immediately. This standardized solution is called spanning tree protocol stp. The basic function of stp is to prevent bridge loops and the broadcast radiation that results from them.
Stp overview stp is a layer 2 link management protocol that prov ides path redundancy while preventing loops in the network. Spanning tree protocol this document descibes spanning tree protocol stp in a wireless environment. Spanning tree enabled switches go through a root election process based on bridge p rotocol data unit. Most lans are designed to provide redundancy so that if a read more. Download pdf stp spanning tree protocol step by step configuration tutorial when sw3 start receiving inferior bpdus at its interface from sw2, switch3 would ignore the inferior information until the bpdus stored with the blocked port expires max age timer 20 seconds. Spanning tree protocol stp is a layer 2 protocol that runs on switches. Pdf rapid spanning tree protocol rstp tutorial jhon. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks.
This is because layer 2 ethernet frameshave no time to live or time out mechanismbuilt into the frame. Introduction to spanningtree spanning tree is a protocol that runs on our switches that helps us to solve loops. Trill transparent interconnection of lots of links is an ietf standard implemented by devices called rbridges routing bridges or trill switches. Stp is on by default, but it only really comes alive when we have two or more switches interconnected with each other. The spanning tree protocol stp is layer 2 protocol. In this spanning tree protocol tutorial, i will present in simplest terms the operation of stp and indicate how.
Stp automatically shut down the redundant links which creates the loops. Stp spanning tree protocol step by step configuration. Spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches. When you connect two or more layer 2 devices, an election is run to designate the root bridge. Rapid spanning tree protocol rstp one big disadvantage of stp is the low. Digital equipment corporation created a protocol called spanning tree protocol stp to prevent broadcast storms and network loops at layer 2. Cisco switching and spanning tree protocol stp basics. The spanning tree protocol stp is a method for dynamically calculating the best spanning tree of a computer network with or without loops. It was first introduced as cst common spanning protocol then ieee introduced its advanced version as stp with specification ieee 802. Stp, rstp, and mstp page 3 overview of spanning trees overview of spanning trees the concept of the spanning tree protocol was devised to address broadcast storming.
Types of spanning tree protocol tutorial and example. Multiple spanning tree multiple spanning tree protocol mstp network organized in regions regions have their own multiple spanning tree instances spanning tree topologies vlans are associated to mstis one common spanning tree cst for the entire network mstp based on rstp rapid stp. Spanning tree also allows a network design to include backup links providing fault tolerance if an active link fails. Spanning tree protocol stp provide the loop avoidance in a network, where multiple switches are connected with each other as shown in below image.
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