Spanning tree protocol explained step by step youtube. Redundant links are found when the switch receives its own bpdu. The switch sends bpdus bridge protocol data units out every active port once every 2 seconds so as to find a redundant link. Before we talk about spanning tree protocol, lets organize the different variants of stp. Aug 04, 2011 the spanning tree protocol stp is a network protocol that ensures a loopfree topology for any bridged ethernet local area network. Vlans must be assigned to a socalled multiple spanning tree. First, it prevents problems caused by loops on a network. The spanning tree map plugin display a graphical map of the bridgesswitches and help the adminitsrator to performs a real time monitoring of the links. Jan 31, 2016 hi guys, this post got awarded best publication at the cisco support community.
This article is related to stp interview questions. In this article, we will try to understand the basic concepts of spanning tree protocols and their implementation. When stp was developed, the concept of a vlan had not even entered anyones thoughts. Furthermore, the administrator can define alternate paths within a spanning tree. Spanning tree also allows a network design to include spare redundant links to provide automatic backup paths if an active. Dec 11, 2019 spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches. The switch with the lowest root cost, as com pared with the other switches attached to the same link, is placed in forwarding state. The main purpose of stp is to ensure that you do not create loops. Spanning trees are important in parallel and distributed computing, as a way of maintaining communications between a set of processors. 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.
Mar 12, 2018 spanning tree protocol stp is a link management protocol preventing media access control mac bridge loops and broadcast delays on any ethernet local area network lan. Many people struggle with stp so in this video, we try to break it down as much as possible. If we tried to continue, the next edge be could not be added because it does not connect two trees, and neither can ce. Spanning tree loop detection is still in operation, however, and the port moves into the blocking state if a loop is ever detected on the port. The basic function of stp is to prevent bridge loops and ensuing broadcast radiation. 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. Consider, city network as a huge graph and now plans to deploy telephone lines in such a. There are no specific requirements for this document.
New users may click register button to join with it core elite members zone. The ieee version was adapted for use with multiple vlans using 802. Read more about the spanning tree protocol on wikipedia. Stp intelligently chooses which ports block, with two goals in mind. Spanning tree protocol concepts and configuration spanning. A key concept about spanning tree protocols on the bigip system is the concept of protocol degradation. It is a fast converged version of spanning tree protocol as its name implies. 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. Rstp bypass the blocking state and listenning state of stp, and provide forwarding state in 15 seconds. Spanning tree protocol concepts and configuration article description when designing a switched network, one of the biggest issues that needs to be dealt with is loop prevention. Configuring stp protocol techlibrary juniper networks. The focus of this topic is to describe how spanning tree protocol can solve common looping problems in a redundant switched network. Abbreviated stp, a link management protocol that is part of the ieee 802. Spanning tree also allows a network design to include backup links providing fault tolerance if an active link fails.
Second, when redundant loops are planned on a network, stp deals with remediation of network. Spanning tree is basically used to find a minimum path to connect all nodes in a graph. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology. You may encounter an issue when implementing a vlan on a network which supports spanning tree protocol stp. A redundant link is usually created for backup purposes. The definition, working, uses and limitations of stp are discussed. Spanning tree protocol concept s 49 that switch is the designated switch, and that switchs interface, attached to that seg ment, is called the designated port dp. Just like every coin has two sides, a redundant link. With stp enabled, some switches block ports so that these ports do not forward frames. Once the root switch is elected, each of the ports is given a role depending on its place within the stp topology. Spanning tree protocol stp is a layer 2 protocol that prevents loops among the networking devices on various network segments. Spanning tree protocol concept s this chapter covers the following exam topics. For purposes of this document, as implemented by the ieee 802.
Bpdu guard is a common feature to use at the same time as portfast, because it watches for incoming bridge protocol data units bpdu, which should not happen on an access port, and prevents the loops from a. Bridge loops are network loops created by multiple active station paths. Here are some most important questions and answer related to stp spanning tree protocol. Understanding the spanning tree protocol stp beaming. When too many computers try to send at the same time, overall network performance is affected and can bring all traffic to a near halt. Rootthe port given this role is the selected best path to reach the root switch. Understanding stp, understanding system identifiers for bridges in stp or rstp instances, configuring stp on ex series switches cli procedure x help us improve your experience. However, the depthfirst and breadthfirst methods for constructing spanning trees. This reduces the number of spanning tree instances required in a switched network with many vlans. I have two book both show different output for the same command show spanning tree vlan idfor a switch running stp. Stp is a data link layer protocol standardized by the institute of electrical and electronics. Stp recognizes the concept of a single root bridge, spanning out to a single flood path, blocking redundant paths to prevent data loops, and bringing blocked paths back into use in the event of primary link failure. The spanning tree algorithm itself is defined by the ieee standard 802.
Today i will explain how switches learn the hardware address of hosts attached to them and how they use this information to perform their tasks. A shared spanning tree, sometimes called mono spanning tree mst by cisco, or more often common spanning tree cst was used to create a single loopfree topology. Using the spanning tree algorithm, stp provides path redundancy while preventing undesirable loops in a network that are created by multiple active paths between stations. How stp works video by sikandar shaik dual ccie rs. Protocol degradation occurs when the spanning tree mode on the bigip system is set to mstp or rstp, but the system detects legacy bridges that is, bridges running an older protocol type on the network. Spanning tree protocol stp was developed before switches were created in.
Multiple spanning tree protocol mstp, initially defined in ieee 802. Understanding spanning tree protocols stp, rstp, mstp. Stp spanning tree protocol automatically removes layer 2 switching loops by shutting down the redundant links. Understanding and configuring spanning tree protocol stp on. Bridges will perform the spanning tree algorithm when they are first connected to the network or whenever there is a topology change. The spanning tree protocol stp was introduced into the networking world as a means to prevent layer 2 network loops frame broadcast storms from disrupting the service of a local area network. Stp spanning tree protocol explained with examples. Rstp excellent summary of rapid spanning tree protocol. When vlans started to become popular, the issue with mixing these two technologies. Spanning tree protocol stp and vlan interaction dummies. Spanningtree protocol overview techlibrary juniper networks.
The main purpose of stp is to ensure that you do not create loops when you have redundant paths in your network. Spanning tree protocol stp is a link management protocol that provides path redundancy while preventing undesirable loops in the network. Ex series,qfx series,mx series,srx series,m series,nfx series,t series,acx series. Hi friends check out below link its my own video tutorial for. By default, portfast is disabled on all switch ports.
Apr 17, 2007 multiple spanning tree mst is an ieee standard inspired from the cisco proprietary multiple instances spanning tree protocol mistp implementation. Stp allows this exception when the link is known to have no switch on the other end of the link, removing the risk of a switching loop. Most asked stp interview questions spanning tree protocols. Spanning tree protocol stp is a big topic on the ccna exam. Stp uses clever mechanisms to prevent loops by virtually disconnecting redundant links. Note in discussions about stp, the term root is used to describe two concepts. Paid members may click log in button to get access. Just like every coin has two sides, a redundant link, along with several advantages, has some disadvantages. The basic function of stp is to prevent bridge loops and the broadcast radiation that results from them. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks.
How spanning tree protocols work, choosing a spanning tree protocol. Aug 31, 2019 spanning tree protocol is a very important concept to understand in networking field. Mar 14, 2015 mohamed samir cisco expertccnp switching course 300115 spanning tree concept cst. To finds a redundant link, it uses an algorithm, known as the sta spanningtree. In this video tutorial i will discuss about basic concept of spanning tree protocol in tamil. Rapid spanning tree protocol rstp is the second stp type. Understanding the spanning tree protocol technical. Stp was created to avoid the problems that arise when computers compete for the ability to use the shared telecommunications path on a local area network. When a bridge hears a configuration message, a special type of bpdu bridge protocol data unit, it will begin its disruptive spanning tree algorithm. Many people struggle with stp so in this video, we try to break it down as much.
On this map, all devices behaving as bridge are represented. Spanning tree protocol stp is a layer 2 network protocol used to prevent looping within a network topology. And these are very helpful for your networking related job interviews. Spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches. A redundant link is an additional link between two switches. Spanning tree protocol concepts and configuration cisco press. 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. You can configure portfast as a global default, affecting all switch ports with a single command. The spanning tree algorithm, chooses a single switch as the root bridge and it uses it as a reference for all path calculation. This table shows the support for mst in various catalyst switches. Stp puts these ports without a role into blocking state, which means these are.
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