As layer 2 networks grew, it quickly became evident that a system to prevent loops was needed if lans were to continue to function. Rapid spanning tree protocol rstp one big disadvantage of stp is the low. Pdf rapid spanning tree protocol rstp tutorial jhon. So therefore, if there is a tie in our value with spanningtree protocol, there has to be a tiebreaker mechanism. This is because layer 2 ethernet frameshave no time to live or time out mechanismbuilt into the frame. What is spanning tree protocol stp sysnettech solutions. Root selection varies depending on the bid of each switch in your lab resulting in varying outputs. Stp will identify if there are any loops, and then disable or block. Spanning tree enabled switches go through a root election process based on bridge p rotocol data unit. For an ethernet network to function properly, only one active.
The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks. 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. Spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. 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. Spanningtree protocol is a link management protocol that provides path redundancy while preventing undesirable loops in the network. Loops are created when multiple paths exist between two. 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. There are the following types of spanning tree protocol 1. This standardized solution is called spanning tree protocol stp. Trill combines techniques from bridging and routing and is the application of link state routing to the vlanaware customerbridging problem. Understanding spanning tree protocol this section describes how spanning tree features work. 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. Spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches.
The different terms in the stp model are explained here. Infrastructure devices such as wireless bridges and switches send and receive spanningtree frames, called bridge protocol data units bpdus, at regular. Digital equipment corporation created a protocol called spanning tree protocol stp to prevent broadcast storms and network loops at layer 2. Redundant network designs allows service continuity in case of link failure.
This article explain the spanning tree protocol stp. 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 standardized as ieee 802. Spanning tree protocol stp determines the least cost path from the root bridge to other nodes in the networks.
Spanning tree protocol stp is a big topic on the ccna exam. The spanning tree algorithm itself is defined by the ieee standard 802. Uplinkfast is used to improve the convergence time of stp in case of a link failure. 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.
Loops and duplicate frames can have severe consequences on a network. Spanning tree protocol in layer 2layer 3 environments. When you connect two or more layer 2 devices, an election is run to designate the root bridge. The spanning tree protocol stp is a method for dynamically calculating the best spanning tree of a computer network with or without loops. Before reading this article you should understand how stp works. The spanning tree protocol stp is layer 2 protocol. Cisco switching and spanning tree protocol stp basics. Cisco developed, implemented and published the per vlan spanning tree pvst proprietary protocol using its own proprietary inter switch.
It is quite useful and should be enabled on the switch interfaces. 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. This tutorial explains what the stp protocol is and how it removes loops from the network. In this spanning tree protocol tutorial, i will present in simplest terms the operation of stp and indicate how. 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. 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. 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. Stp automatically shut down the redundant links which creates the loops. Trill transparent interconnection of lots of links is an ietf standard implemented by devices called rbridges routing bridges or trill switches. Spanning tree protocol stp is a layer 2 protocol that runs on switches. Tutorial on stp, spanning tree protocol algorithm, which finds the minimum spanning tree for packet forwarding between switches in a network.
The problem is that when we create redundancyat a layer 2 level of our networks,we create loops that traffic will traverse indefinitely. The golden rule of spanningtree protocol is lower is better. Spanning tree protocol stp spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. Many people struggle with stp so in this video, we try to break it down as much. Therefore, the switch2 and switch3 ethernet0 0 interfaces above will be configured as root ports. 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. In spanning tree protocol configuration, the shortest path to the root bridge switch is called the root port. Stp overview stp is a layer 2 link management protocol that prov ides path redundancy while preventing loops in the network. 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. Stp, otherwise known as the spanning tree protocol 802. Stp is on by default, but it only really comes alive when we have two or more switches interconnected with each other. 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.
Types of spanning tree protocol tutorial and example. Spanning tree is basically used to find a minimum path to connect all nodes in a graph. 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. 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. However, the most common you will encounter will be loops. Spanning tree also allows a network design to include spare redundant links to provide automatic backup paths if an active link fails. Most lans are designed to provide redundancy so that if a read more. Spanning tree protocol uses a clever mechanism or algorithms. Spanning tree also allows a network design to include backup links providing fault tolerance if an active link fails. Ccna training spanning tree protocol stp tutorial 9tut. Spanning tree root port is used to select path cost. On each switch, display the spanning tree table with the show spanning tree command.
There are two famous algorithms for finding the minimum spanning tree. Switches running stp will build a map or topology of the entire switching 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 mstp based on rstp rapid stp. Spanning tree protocol stp provide the loop avoidance in a network, where multiple switches are connected with each other as shown in below image. The spanning tree portfast is introduced to avoid the network connectivity issues. Introduction to spanning tree protocol stp in bigger networks, having a redundant design is crucial. Rbridges are compatible with and can incrementally replace previous ieee 802. Learn stp features and functions in detail with examples. Understanding and configuring spanning tree protocol stp.
Enabling the portfast causes the switch or trunk port to enter the stp forwardingstate immediately. You will learn how spanning tree works and how you can verify the spanning tree config on cisco switches. Spanning tree protocol this document descibes spanning tree protocol stp in a wireless environment. Stp spanning tree protocol step by step configuration. Stp spanning tree protocol explained with examples. Consider, city network as a huge graph and now plans to deploy telephone lines in such a. Introduction to spanningtree spanning tree is a protocol that runs on our switches that helps us to solve loops. Supermicro l2l3 switches configuration guide 5 spanning tree enabled switches exchange spanning tree protocol messages bpdu to form a loopfree topology. The basic function of stp is to prevent bridge loops and the broadcast radiation that results from them. Spanning tree protocol explained step by step youtube. Dell networking and cisco spanningtree interoperability. Root selection varies depending on the bid of each switch in your lab. Spanning tree protocol through softwaredefined networking tutorial fabiobentostpmininetryu tutorial.
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