Different root switches and different stp parameters can be individually configured for each msti. Edc0 hello time 2 sec max age 20 sec forward delay 15 sec aging time 20 interface role sts cost prio. Stp is a layer 2 link management protocol that provides path redundancy while. 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. Spanning tree protocol stp page 6 spanning tree protocols. First, it prevents problems caused by loops on a network. The node with the smallest id is selected the root bridge 2. In this spanning tree protocol tutorial, i will present in simplest terms the operation of stp and indicate how this protocol prevents the creation of bridging loops. And so, dont be too confused when we say root switch or root bridge, they are the same, they are the same. In this article, we will try to understand the basic concepts of spanning tree protocols and their implementation. Understanding spanning tree protocol this section describes how spanningtree features work.
Perlman devised a method by which bridges can obtain layer 2 routing utopia. This section describes how spanningtree features work. Spanning tree protocol is standardized as ieee 802. The basic function of stp is to prevent bridge loops and the broadcast radiation that results from them. On each switch, display the spanning tree table with the show spanningtree command. Radia perlman, distinguished engineer at sun microsystems.
This protocol also allows a network design to include redundant links for providing automatic backup paths. 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. Spanning tree protocol stp spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. Cisco spanning tree protocol guide stp examples and. Switches running stp will build a map or topology of the entire switching network. What is spanning tree protocol stp sysnettech solutions. Im implementing hsrp on core switch in my network, but spanning tree always block one port on the layer 2 switch. 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. This standardized solution is called spanning tree protocol stp. Algorithm that creates a loopfree logical topology.
Spanningtree protocol stp has nowadays been implemented by most manufacturers in order to avoid loops in bridged networks. Stp spanning tree protocol chooses the best path as well as preventing loops on the network. Download spanning tree protocol interview questions and. Spanning tree protocol stp is a layer 2 network protocol used to prevent looping within a network topology. At this point, stp spanning tree protocol will come into play. Spanning tree also allows a network design to include spare redundant links to provide automatic backup paths if an active link fails. Rapid spanning tree protocol rstprstp is defined in ieee 802. In this article, i am going to explain all the terms, concepts and working of spanning tree protocol stp with the example, i have tried to clear all the concepts and doubts which usually rises in the spanning tree protocol so, if you are interested to know something more about spanning tree protocol keep reading this article till the end.
Spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. Introduction to spanning tree protocol contemporary controls. We will focus on spanning tree protocol stp configuration and verification commands in this tutorial, as implemented on cisco. Cisco introduced several enhancements to the standard stp operation that were later incorporated in rapid spanning tree protocol rstp defined as ieee 802. Vlan0005 spanning tree enabled protocol ieee root id priority 32773 address 00. Stp spanning tree protocol automatically removes layer 2 switching loops by shutting down the redundant links.
Stp port states in stp mode, each switch port can be in one of five spanning tree states, and one of two. Spt is employed for the prevention of bridge loops and the broad cast radiation of them. Stp will identify if there are any loops, and then disable or block. Fundamentals of stp spanning tree protocol part i the logic. Mstp multiple spanning tree protocol can map a group of vlans into a single multiple spanning tree instance msti. Which means, the spanning tree protocol is applied separately for a set of vlans instead of the whole network. To view the information about the stp operation, you can use the show spanningtree command from the privilegedexec mode. The spanning tree protocol stp is a network protocol that ensures a loopfree topology for any bridged ethernet local area network. Once the root switch is elected, each of the ports is given a role depending on its place within the stp topology. To create a loopfree tree, bridges in the network exchange bpdus, and execute the spanning tree protocol as follows.
Spanning tree protocol variants best cisco ccna ccnp and. Rootthe port given this role is the selected best path to reach the root switch. The basic function of stp is to prevent bridge loops and ensuing broadcast radiation. Root selection varies depending on the bid of each switch in your lab. Tp, which stands for spanning tree protocol, is a network layer protocol that helps in building a logical loopfree topology for the ethernet networks many enhanced versions of stp kept on. The spanning tree algorithm itself is defined by the ieee standard 802. Second, when redundant loops are planned on a network, stp deals with remediation of network. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks. The following image shows how the stp changes a physically looped topology into a virtually looped free topology. The following table lists some of the differences among the. 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. Spanning tree protocol timing protocol is timer driven too short timers can give loops and instabilities too long timers can give long convergence. So the same nomenclature for the different reference points lives to this day.
The main purpose of stp is to ensure that you do not create. Stp, rstp, and mstp spanning tree protocol stp stp uses the process described in table 1 on page 4, to avoid loops. 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. Example of a bridged network with a loop, and the minimum spanning tree with the loop removed. Stp spanning tree protocol explained with examples. When too many computers try to send at the same time, overall network performance is affected and can bring all traffic to a near. 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. To enable spanning tree, connect to your switch and type spanningtree mode while in global configuration mode. This protocol was created by radia perlman for bridges, ethernet transparent bridges. Edc0 this bridge is the root hello time 2 sec max age 20 sec forward delay 15 sec bridge id priority 32769 priority 32768 sysidext 1 address 0001.
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. Observe the response to a change in the spanning tree topology. The output of this command can be divided into three subsets. The stp uses the spanning tree algorithm sta algorithm to avoid loops. The original stp was developed by radia perlman while working for dce back in 1990. Before we talk about spanning tree protocol, lets organize the different variants of stp.
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. Pdf formal specification of spanning tree protocol using acp. You will learn how spanningtree works and how you can verify the spanningtree config on cisco switches. This technology case study focuses on spanning tree protocol stp. Observe and explain the default behavior of spanning tree protocol stp, 802. Arista switches support the leading spanning tree protocols. Introduction this implementation guide will provide a basic understanding of all three versions of the spanning tree protocol, namely 802. Understanding and configuring spanning tree protocol stp. As the name implies, stp, spans all switches in a network or subnet.
Spanning tree protocol in layer 2layer 3 environments. Spanning tree protocol stp is a layer 2 protocol that runs on switches. The flavor of spanning tree protocol, we have been discussing, so far in this module has been the traditional 802. Pdf spanningtree protocol stp has nowadays been implemented by most manufacturers in order to avoid loops in bridged networks. Stp path cost automatically changes when a port speedduplex is changed troubleshoot commands command summary related information introduction spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches. Although the operational logic of the stp is mainly mixed, it is very easy to configure on switches. Understanding spanning tree protocols stp, rstp, mstp. It was first introduced as cst common spanning protocol then ieee introduced its advanced version as stp with specification ieee 802. Cable a network that is similar to the one in the topology diagram. As a result, the switch generates untagged bridge protocol.
All switches from cisco ship with spanning tree protocol stp enabled by default, but if stp is misconfigured for any reason, you can easily enable it. 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 spanning tree overview 1461 the following sections describe spanning tree configuration parameters. Spanning tree protocol spt is a network protocol which make sure of loopfree topology for any bridged ethernet local area network.
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