Spanning tree protocol stp spanning tree protocol stp was developed to prevent the broadcast storms caused by switching loops. Spanning tree protocol runs on switches and bridges on a lan. Stp will identify if there are any loops, and then disable or block. Jul 06, 2015 stp uses spanning tree algorithm sta to create a topology database of a network and then search out and disable redundant links. This chapter describes how to configure spanning tree protocol stp parameters on hp procurve routing. Configure spanning tree protocol stp part1 wael osama july 24, 2008 as we mentioned in one of our previous posts, stp was developed to allow redundancy in the l2 network while maintaining a loop free network. It should take about 1 hour to run this experiment. Spanning tree protocol stp is a layer 2 protocol that runs on switches.
Stp spanning tree protocol step by step configuration. Lan switching configuration guide spanning tree protocol. Spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches. The standard also includes features equivalent to cisco portfast, uplinkfast and backbonefast for faster network reconvergence. Before jumping deep into spanning tree protocol configuration, i am going to discuss some important terms related to stp. Spanning tree protocol timing protocol is timer driven too short timers can give loops and instabilities too long timers can give long convergence times until network reaches a stable spanning tree configuration proto id 2 root id 8 ver 1 bpdu type 1 flags 1 root path cost 4 bridge id 8 port id 2 msg age 2 max age 2 hello time 2. If not, check for missing configuration statements. To fix the problem, either agg2 would have to take over as the root bridge, or you would need to enable the fhrp protocol on agg1. A redundant link is usually created for backup purposes. For more information about the default spanning tree protocol settings, see configure spanning tree protocol settings in the cli. For additional information about source routing and the spanningtree protocol, we recommend the following reference material the ibm titles are available from an ibm representative or ibm branch office.
Once a stable network topology has been established, all bridges listen for hello bpdus bridge protocol data units transmitted from the. This chapter explains the protocol, or grammar, of communication between switches. Switches connected in an actual loop topology in todays networks are rare. This series of tutorial videos on the spanning tree protocol stp dymsytifies and explains some of things that ccna candidates will need to know to pass certification exams. The spanning tree protocol, or stp, is a linkmanagement protocol that is part of the institute of electrical and electronics engineers ieee 802. For additional information about source routing and the spanning tree protocol, we recommend the following reference material the ibm titles are available from an ibm representative or ibm branch office. Spanning tree protocol maintains a loopfree networkby pruning redundant links and monitors the stateof the network and will change the pathwaysto fit the current link conditions in orderto keep it operational. A network administrator can reduce the cost of a spanning tree, if necessary, by altering some of the configuration parameters in such a way as to affect the choice of the root of the spanning tree. Stpaware devices exchange bridge protocol data units bpdus periodically.
These messages are called bpdus bridge protocol data units. The need for the spanning tree protocol stp arose because switches in local area networks lans are often interconnected using redundant links to improve resilience should one connection fail 386 however, this connection configuration creates a switching loop resulting in broadcast radiations and mac table instability 388 if redundant links are used to connect switches, then switching. A key protocol used to maintain efficiency within a lan is the spanning tree protocol stp, which is standardized as ieee 802. Instructor spanning tree protocol is used ona local area network because in most casesswitches have redundant links for fault tolerance. The latest version of spanning tree is rstp, this is 802. If you havent seen it before, i would recommend to look at it first before diving in the configuration. The bpdus communicate and compute the spanning tree topology. The root bridge is special because all the path calculation through the network is based on the root.
Second, when redundant loops are planned on a network, stp deals with remediation of network. But stp can save you from consequences of a potential human error, such as port channel misconfiguration. This command exits mst configuration mode and saves all pending changes. Stp spanning tree protocol automatically removes layer 2 switching loops by shutting down the redundant links.
A redundant link is an additional link between two switches. 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. Lesson 21 spanningtree protocol in practice previous post was designed to present in a nutshell the stp operation. Understanding and configuring spanning tree protocol stp on. When you connect two or more layer 2 devices, an election is run to designate the root bridge. I think it is a good idea to look at the same concepts using real equipment. The problem of the suboptimal route that the ip packets take from the server to the gateway agg2 in figure 6 results from a spanning tree blocking connections for all routed packets through agg1. Spanning tree protocol stp stp often accounts for more than 50 % of the configuration, troubleshooting, and maintenance headaches in real world campus networks especially if they are poorly designed. Aug 29, 2017 spanning tree protocol stp is a big topic on the ccna exam.
It was first introduced as cst common spanning protocol then ieee introduced its advanced version as stp with specification ieee 802. Spanning tree protocol stp is a layer 2 network protocol used to prevent looping within a network topology. The spanning tree that the bridges compute using the spanning tree protocol can be. Spanning tree elects one bridge on the lan to be the master bridge. Spanning tree enabled switches exchange spanning tree protocol messages bpdu to form a loopfree. Figure 3 there are two types of bridge protocol data unit types. Next, the administrator will identify root ports and designated ports. Sep 25, 2014 this series of tutorial videos on the spanning tree protocol stp dymsytifies and explains some of things that ccna candidates will need to know to pass certification exams. 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 in layer 2layer 3 environments. Because spanning tree protocol operates on layer 2 of your network, you can enable this feature without any impact to firebox performance. Spanning tree protocol spanning tree overview 1455 the following sections describe spanning tree configuration parameters.
We will also see how the spanning tree protocol reacts when the topology changes. Cisco ccnp switch multiple spanning tree protocol mst rapid spanning tree protocol rstp is an evolution of the spanning tree protocol 802. Avoids loops by reducing network connectivity reacts to changes in the network topology either good news or bad news is completely transparent to the user stp implements fault tolerance at data link level. It is quite useful and should be enabled on the switch interfaces. The election decides which switch will become the root bridge, as well as the.
Without this protocol our lans would rapidly become congested, with frames looping throughout the network infinitely, making network devices unstable. 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 also allows a network design to include spare redundant links to provide automatic backup paths if an active. Spanning tree protocol stp is a big topic on the ccna exam. Spanning tree protocol stp helps to prevent network topology loops and is highly recommended for use in any network.
Introducing spanning tree protocol as with traditional shared ethernet, transparent bridges inherently lack the capability to provide redundancy. Indeed there is and an example would be the spanning tree protocol. Automatic reconfiguration of tree in case of topology changes e. You can map this ip protocol to the networking layer, and that in turn is associated with routers. The spanning tree that the bridges compute using the spanning tree protocol can be determined using the following rules. Are there any other protocols associated with hardware devices. Spanning tree was great when it came out in 1990, but there have been a number of changes to networking and a number of changes to spanning tree through the years. Spanning tree also allows a network design to include spare redundant links to provide automatic backup paths if an active link fails.
However, without some practice its just academic knowledge. Switches running stp will build a map or topology of the entire switching network. The spanning tree protocol run my experiment on geni. Dec 22, 2012 spanning tree protocol stp stp often accounts for more than 50 % of the configuration, troubleshooting, and maintenance headaches in real world campus networks especially if they are poorly designed. In this document, provider edge pe devices in a redundancy group rg running iccp are used to offer multihomed connectivity to spanning tree protocol stp networks to improve availability of the stp networks. Configuring spanning tree protocol stp ftp directory listing. Now that youve seen the overview of how you can prevent loops with the spanning tree protocol, continue your learning with these stp resources. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks. Root selection varies depending on the bid of each switch in your lab resulting in varying outputs. The network administrator then adjusts spanning tree operation to control its behavior by first electing a root bridge, which becomes the central reference point for stp. On each switch, display the spanning tree table with the show spanningtree command. A catalyst 4500 series switch use stp the ieee 802. Bridge program users guide this guide accompanies the ibm tokenring network bridge program, version 2.
The basic function of stp is to prevent bridge loops and ensuing broadcast radiation. February 2006 page 3 spanning tree protocol info sheet. The spanning tree protocol stp inserts a mechanism into the ethernet transparent bridge environment to dynamically discover the network topology and ensure only one path through the network. Pervlan spanning tree protocol pvst is maintaining a spanningtree instance for each vlan configured in the network and uses ciscos proprietary isl trunking protocol. Spanning tree protocol how the spanning tree protocol organizes an ethernet network. Stp spanning tree protocol explained with examples. This protocol is a layer two layer two data link layer protocol that is associated with switches and bridges. 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. Rapid spanning tree protocol the intel pro set ieee rapid spanning tree protocol rstp can be used alongside 802. If you havent seen it before, i would recommend to look at it first before diving in the configuration having said that, lets look at the configuration. How to configure spanning tree protocol offers an overview of stp configuration. Spanning tree protocol understanding spanning tree protocol 3 cisco 3200 series wireless mic software configuration guide when the bridges in a network are powered up, each br idge functions as the stp root. 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. The interchassis communication protocol iccp supports an inter chassis redundancy mechanism that is used to support high network availability.
The bridges send configuration bpdus through the ethernet and radio ports. Lesson 3 initial configuration of cisco switch and router. Spanning tree protocol stp is not supported from junos os release 15. The necessary commands on interface configuration level, that you need in order to achieve this are. Understanding and configuring spanning tree protocol stp. On each switch, display the spanning tree table with the show spanning tree command. Spanning tree protocol understanding spanning tree protocol 2 cisco 3200 series wireless mic software configuration guide stp forces redundant data paths into a standby blocked state. Spanning tree protocol, or stp, prevents switching loops in the layer 2 portion of our network. A number of different stp standards and protocols evolved over time. By default, a single spanning tree runs on each configured vlan provided. Complex protocol that is generally poorly understood. Just like every coin has two sides, a redundant link, along with several advantages, has some disadvantages.
Many people struggle with stp so in this video, we try to break it down as much as possible. The main purpose of stp is to ensure that switches do not create loops when they have redundant paths in a network. In a previous lesson i explained the differences between classic and rapid spanningtree and how rapid spanningtree works. Stp is on by default, but it only really comes alive when we have two or more switches interconnected with each other. Rfc 7727 spanning tree protocol stp application of the. This is spanning tree standard called rapid spanning tree protocol. 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 interoperability with cisco arista networks. Understanding the spanning tree protocol technical. 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. Once a stable network topology has been established, all bridges listen for hello bpdus bridge protocol data units transmitted from the root bridge. Dec 11, 2019 spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches. The spanning tree algorithm itself is defined by the ieee standard 802.
Spanning tree protocol explained step by step youtube. Spanning treeenabled switches go through a root election process based on bridge p rotocol data unit. Spanningtree protocol, or stp, prevents switching loops in the layer 2 portion of our network. When the bridged lan topology changes, a new spanning tree is constructed. Abcs of spanning tree protocol contemporary controls. In this configuration, the original spanning tree algorithm results in a suboptimal path from the server to the gateway.
If a network segm ent in the spanning tree fails and a redundant path exists, the spanningtree algorithm recalculates the spanningtree topology. Pvst can load balance traffic at layer 2 of the osi model without causing a loop. Configuration bpdu the unique bridge id of the root device in the network the stp path cost to the root the bridge id of the transmitting bridge the identifier of the transmitting port values for the. Cisco nexus 5000 series switch cli software configuration guide ol1659701 1 configuring mst multiple spanning tree mst, which is the ieee 802. Stp uses these configuration messages bpdus as it transitions port states to achieve convergence. First, it prevents problems caused by loops on a network. Spanning tree protocol understand stp principles, redundant. The spanning tree protocol stp is a network protocol that ensures a loopfree topology for any bridged ethernet local area network. I e e e s standards are rapid spanning tree protocol rstp and multiple stp mstp. Media in category spanning tree protocol the following 21 files are in this category, out of 21 total. The assignment of forwarding and blocking ports are same in both stp and rstp, the main reason to use rstp is to overcome the. Rapid spanning tree protocol improved stp with faster convergence backward compatible with stp rstp ieee 802. Spanning tree protocol overview presented by arash foroughi iran, november 2015 2.
545 1491 119 759 1198 718 1338 549 75 413 1106 670 1300 945 628 1125 1433 917 1191 1087 1119 576 366 1266 289 1549 563 1098 770 1538 945 1131 1574 1058 1002 999 52 1114 673 94 963 516 256 372