Spanning tree protocol, rapid stp port costs port states. If the ms switch is configured to use stp, an entry will appear in the event log whenever a ports stp status changes. Ieee added these features in a new stp protocol called rapid spanning tree protocol rstp under the 802. I have read plenty of explanations but none that explains it clearly. The basic function of stp is to prevent bridge loops and ensuing broadcast radiation. What would be five different states through which ports on a switch running stp can transition.
None of the ports will transmit or receive any data, but they will listen to bpdus. Ccna training rapid spanning tree protocol rstp tutorial. Spanning treeenabled switches go through a root election process based on bridge p rotocol data unit. A nondesignated port is a port that has the higher port cost than the designated port. Notice that fa020 has a role of designated port with state as forwarding.
Read how do all the operations happen and what are the chief components of the same. Free cisco certified network associate ccna online. Jul 11, 2012 learn what happens during each spanning tree protocol port state and why they are needed for stp operation. You can configure stprstp on an ethernet network to ensure that the network has a loop free tree topology.
Spanning tree protocol this document descibes spanning tree protocol stp in a wireless environment. Stp can be difficult to understand and the following sections look deeper into various aspects of it. The stp port states disabled, blocking and listening were merged into the rstp. This time, different port states in spanningtree protocol naman ang paguusapan natin. It is always recommended to manually set up each bridges priority, port priority, and port path cost to ensure proper layer2 functionality at all times. Spanning tree port states if you have played with some cisco switches before you might have noticed that every time you plug in a cable the led above the interface was orange and after a while became green. As of rstp, the protocol now includes not only states learning, forwarding and discarding and roles designated, root, alternate, backup and master for mst. Oct 18, 2017 in this video i am showing you what is stp spanning tree protocol in tamil why do we have a loop.
Stp relies on the exchange of bpdus to maintain a loop free environment. Blocked, listening, learning, forwarding, disabled. The way it does this is by controlling the redundant links that connect into the same network segment. Thus, stp will set the s1 port fa01 to a blocking state, and the trunk link trunk2 will not forward any traffic. Rstp expends the stp port roles by adding the alternate and backup roles. Configuring remarking of destination mac addresses. Spanning tree protocol stp is a layer 2 protocol that runs on bridges. The focus of this topic is to describe how spanning tree protocol can solve common looping problems in a redundant switched network. Stp allows bridges and switches to communicate with each other so they can create a loop free. Understanding issues related to intervlan bridging pdf.
Spt must performs three steps to provide a loop free network topology. What is the name of the rstp port state that combines the stp disabled, blocking and listening states. Spanningtree bridge assurance is one of those stp features that help to prevent bridging loops in your network. Cisco protocol, duplex connections, stp port states, switches, telnet proprietary cisco layer 2 protocol that uses multicast to gather hardware and protocol information about directly connected devices. The event log entry will display the old state and the new state, where the possible states are. During the switch initial election process in spanningtree protocol, all ports are temporarily in blocking state. Learn about free offerings and business continuity best practices during the covid19 pandemic. One of the topics on the ccna rs version 3 exam is spanning tree protocol stp. If the port is in stp forwarding state in that vlan, use it as normal. Digital equipment corporation created a protocol called spanning tree protocol stp to prevent broadcast storms and network loops at layer 2. In our earlier article we discussed about the spanning tree protocol, rapid stp port costs and port states. Stp is enabled by default on all cisco switches, for all vlans. If you have played with some cisco switches before you might have noticed that every time you plug in a cable the led above the interface was orange and after a while became green. Ports states and transitions for stp are defined by the following state transition diagram.
When stp is enabled in port config, an active port shows under port forwarding mode as being in forwarding. Cms requested additional edits for the sitespecific assessment portion of the stp. The spanning tree protocol addresses this issue in a network with physical loops by setting some redundant paths to a blocked state and leaving others in a forwarding state. Port stp changes reflect the stp state of the port. To overcome this problem, in 2001, the ieee with document 802. When bridge assurance is enabled, bpdus are sent on all interfaces of your switch, including blocked interfaces like the alternate or backup port. Observe how spanning tree protocol transitions ports through several states to safely begin forwarding frames in a loop free fashion. Spanning treeenabled switches go through a root election process based on bridge p.
Yet when stp is disabled, it shows as being in manual forwarding. Rstp use the same timerbased process as stp on pointtopoint links. Free cisco certified network associate routing and switching ccna routing and switching online tutorials and study guides. Stp employs its algorithm and puts certain interfaces in a forwarding state. The main purpose of stp is to prevent switching loops throughout a lan. Stp allows bridges and switches to communicate with each other so they can create a loop free topology.
Stp port states all ports on a stp running switch, go through the four different states. Spanning tree protocol stp determines the least cost path from the root bridge to other nodes in the networks. Timers, in seconds spanningtree mst hellotime 2 spanningtree mst forwardtime 15 spanningtree mst maxage 20. Stp spanning tree protocol explained with examples. When a switch port transitions directly from nonparticipation in the stable topology to the forwarding state.
To create a single path between each ethernet segment, for to and fro communication, stp decides on the state of each ethernet interface. Root bridge stp ports stp port states vlan and dtp in plain english s. You will learn how spanningtree works and how you can verify the spanningtree config on. After configuring stp, we can learn which switch is root bridge or which switch blocked port has with cli commands. Before stp decides which path is the best to the root bridge, it needs to first decide which switch has to be elected as the root bridge, which is where the bridge id comes into play. Stp practice exercise best cisco ccna ccnp and linuxcentos. Use pdf download to do whatever you like with pdf files on the web and regain control. Stp was created in 1985 and is a very old protocol. Configuring stp and rstp this chapter describes the ieee 802. Download free ebooks at ccna in 21 hours 4 contents contents about this book 12 introduction. With stp, you can safely assume that a listening port is either designated or root, and is on its way to the forwarding state. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology. The spanning tree protocol stp is a network protocol that builds a loop free logical topology for ethernet networks.
Difference between stp and rstp difference between. Portfast allows a switch port to bypass the usual progression of stp states. The state of a switch port is taken into account by stp. The basic function of stp is to prevent bridge loops and the broadcast radiation that results from them. In 2001, a new protocol named rstp or rapid spanning tree protocol was created as a successor to stp. Note that these stp states do not change the other information you already know about switch interfaces. Stp port states are disabled, blocking, listening, learning and forwarding. The manual isnt really clear on what this status means, it states. The election of designated port can be influence by changing the cost of the port this concludes a basic overview of stp. This chapter describes how to configure the spanning tree protocol stp and rapid spanning tree protocol rstp. Rstp port states are blocking, discarding, learning, or forwarding. This allows stp to maintain redundancy and faulttolerance.
Discover the three timers utilized by traditional stp. Indiana submitted version 6 of the stp in march 2017 with additional updates and details for remediation, heightened scrutiny, ongoing monitoring, and. Spanning tree also allows a network design to include backup links providing fault tolerance if an active link fails. While spanning tree stp takes more than 30 seconds to move a port to a forwarding state, rstp can move a port to the forwarding state within 3 times of the hello interval the default hello interval is 2 seconds. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks. The whole process is more complex than what is shown above. Figure 2 spanningtree interface states when you enable stp on the bridge, the ethernet and radio interfaces go through the blocking state and the transitory states of li stening and learning. The spanning tree protocol stp is a network protocol that ensures a loop free topology for any bridged ethernet local area network.
Lesson 57 introduction to open shortest path first ospf protocol. Interface attributes interface fastethernet01 spanningtree mst 1 port priority 128 spanningtree mst 1 cost 19 bridge id format pri sys id. Stprstp configuration s12700 v200r010c00 configuration. Figure 2 spanningtree interface states when you enable stp on the bridge, the ethernet and radio interfaces go through the blocking state and.
The blocking state prevents ports from being used to. Stp stab ilizes each interface at th e forwarding or blocking state. Learn vocabulary, terms, and more with flashcards, games, and other study tools. If the ms switch is configured to use stp, an entry will appear in the event log whenever a port s stp status changes. For instance the difference between blocking and listening. Many of the levels include handson lab demonstrations, allowing you to follow.
Routeros is capable of running bridge interfaces with rmstp support in order to create a loop free and layer2 redundant environment. This webcast shows you the stp topics for which youre responsible on the ccna rs 200125 or icnd2 200105. Spanning tree protocol in layer 2layer 3 environments. Rapid spanning tree protocol rstp provides faster topology convergence. The bpdu carries various pieces of information that are used by stp to determine what state the ports. Rapid spanning tree protocol rstp, which significantly reduces the convergence time after a topology change occurs in the network. In addition, we can examine stp portfast, stp uplinkfast and stp backbonefast features with these commands create a redundancy network using the gns3 or cisco packet tracer program and apply the following commands on switch privileged mode to. Stp practice exercise,spanning tree protocol,root bridge, root ports, designated ports,blocking ports,macaddress tiebreaker,switch priority, spanning tree cost, stp cost,stp port id, port priority,lowest port id,stp pdf file, pdf download. A blocked port can be reactivated if another port goes down. On november 8, 2016, cms granted initial approval to indiana s stp for the systemic portion of the plan. What is the name of the common frame of reference used by stp switches to agree on a loop free topology. You will learn how spanningtree works and how you can verify the spanningtree config on cisco switches.
Topology change notification acknowledgment tca bpdus are being sent every 2 seconds so that the switches can keep track of the network changes and to start and stop forwarding at ports. Maximum hops for bpdus spanningtree mst maxhops 20. Stp will identify if there are any loops, and then disable or block as many ports as necessary to eliminate all loops in the topology. Spanning tree protocol overview the plugandplay spanning tree protocol stp, a layer 2 protocol that ensures a loop free topology in bridged lans, has been around for decades. Spanning tree also allows a network design to include spare redundant links to provide automatic backup paths. This creates a loop free logical topology, so that a broadcast storm cannot occur. Through these states, the switch not only understands the network topology but also calculates the path cost value and based on that value elects the designated and nondesignated ports.
Mstp uses bpdus to exchange information between spanningtree compatible devices, to prevent loops in each msti multiple spanning tree instances and in the cist common and. Which is not one of the four steps in operating most. What is happening at this moment is that spanning tree is determining the state of the interface. The multiple spanning tree protocol mstp and algorithm, provides both simple and full connectivity assigned to any given virtual lan vlan throughout a bridged local area network.
Stp facilitates the logical loopfree path throughout the broadcast domain. Spanning tree protocol understanding spanning tree protocol 6 cisco 3200 series wireless mic software configuration guide figure 2 illustrates how an interface moves through the states. Sorry for the many questions, only asking cause like i said in my previous question my knowledge is little in the networking field and any help would be much appreciated. If a switch port transitions directly from the blocking state to the forwarding state without information about the full topology during the transition, the port can temporarily create a data loop. The spanning tree protocol run my experiment on geni. Question 43 what are the three rstp port states choose three. Stp marks the nondesignated port as the blocking port. Thanks for reply so the port in other states gi01 on both switches is it in blocking state on both ends or blocking state on 1 end only. Which protocol provides up to 16 instances of rstp, combines many vlans with the same physical and logical topology into a common rstp instance, and provides support for portfast, bpdu guard, bpdu filter, root guard, and loop guard. Spanning tree protocol stp page 6 spanning tree protocols. Switches running stp will build a map or topology of the entire switching network. The learning and forwarding states are the same as the original stp standard, but the discarding state performs the functions originally performed in the disabled, blocking, and listening stp states.
Listening and learning are transitory port states, used only when moving from the blocking to the forwarding state. One big disadvantage of stp is the low convergence which is very important in switched network. Feb 17, 2012 informs switches of any updown port changes. Pptx to stp, ppt to stp, pdf to stp, sxi to stp, bmp to stp, emf to stp, eps to stp, gif to stp, jpg to stp, met to stp, odd to stp, odg to stp, odp to stp, pbm to stp, pct to stp, pgm to stp, png to stp, pot to stp, ppm to stp, pwp to stp, ras to stp, sda to stp, sdd to stp, sti to. Propagation delays can occur when protocol information is passed through a switched lan. The spanningtree algorithm calculates the best loopfree path throughout a layer 2 network. Lesson 114 how spanning tree protocol stp select designated port.
Port state description root port the port on a nonroot bridge that is closest to the root bridge, in terms of cost designated port the port on a network segment that is closest to the root bridge, in terms of cost nondesignated port ports that block traffic, in order to preserve a loop free. In order to choose the best path for the packets to travel across and to prevent looping, stp or the spanning tree protocol was created. S2 is configured with stp and has set the port for trunk2 to a blocking state. The bridges have to determine the root bridge and compute the port roles root. Stp defines a tree with a root device and a loop free path from the root to all infrastructure devices in. Stp, rstp, and mstp spanning tree protocol stp stp uses the process described in table 1 on page 4, to avoid loops. Jun 27, 2017 the different port states in spanningtree protocol and how they work 1.
Spanning tree protocol, rapid stp port costs and port states are an essential part of the stp algorithm that affect how stp decides to forward or block a port leading to the root bridge. It also explains how to configure stp and rstp on the mlseries card. An interface can only be in two states, forwarding state or blocking state. Alternate port backup for root port backup port backup for designated port on the segment in rstp, all bridges send bpdus automatically while in stp, the root triggers bpdus in rstp, bridges act to bring the network to convergence while in stp, bridges passively wait for timeouts before changing port states. Web to pdf convert any web pages to highquality pdf files while retaining page layout, images, text and. Stp is desinged to fix this allows redundant connections but prevent traffic loops layer3 loops are prevented using mechanisms like split horizon stp solves the looping problem by blocking redundant paths stp tells what interfaces are actively being used to insert mac addresses in the cam table. Instructor and ccie keith bogart walks you through the full range of topics on the ccna icnd2 200105 exam, including lan switching technologies, routing technologies wan technologies, infrastructure services and infrastructure maintenance. Spanning tree protocolstpto prevent switchinglayer2. What would be five different states through which ports on a. Stp port states in stp mode, each switch port can be in one of five spanning tree states, and one of two. All ports on a stp running switch, go through the four different states. Rstp is far superior to stp and should be used in any. The disabled, blocking and learning states have been combined into a new discarding state in rstp. Stp port states in stp mode, each switch port can be in one of five spanning tree states, and one of two switch states.
Understand how these timers are used to carefully transition ports through the various stp states, as well as their role in reacting to topology changes. The stp port states shown in table 2 affect the behavior of ports whose switch state is enabled. As a result, topology changes can take place at different times and at different places in a switched network. Free online presentation converter convert stp to ppt, pdf. Nov 01, 2017 this lesson is an introduction to spanningtree.