Cisco spanning tree protocol guide stp examples and. Once the root switch is elected, each of the ports is given a role depending on its place within the stp topology. The sta algorithm first creates a topology database then it finds and disables the redundant links. In this curriculum, when the original spanning tree protocol is the context of a discussion, the phrase original 802. This means that each vlan is mapped to a single spanning tree instance. Rapid for being a fast version of spanningtree protocol and it was labeled as 802. In example 311, the output shows that the priority for vlan 10 is 4096, the lowest of the three respective vlan priorities. When you have 20 vlans, it means there are 20 instances of spanning tree. Spanning tree protocol stp is a link management protocol that provides path redundancy while preventing undesirable loops in the network.
It vigilantly monitors the network to find all links, making sure that no loops occur by blocking any redundant ones. Because the two protocols share much of the same terminology and methods for the loopfree path, the primary focus is on the current standard and the cisco proprietary. When you connect a cisco switch to a noncisco device that supports 802. Cbt nuggets trainer jeremy cioara explains how to configure spanning tree protocol as well as the different types of spanning tree protocols. Cisco also recommends using link aggregation control protocol lacp as the link aggregation protocol for etherchannel. To configure the cisco 3750 to use mstmultiple spanning tree use the following commands. Cisco spanning tree protocol guide stp examples and configuration spanning tree protocol stp ensures a loopfree topology in a local area network lan made up of switches. It is a fast converged version of spanning tree protocol as its name implies. To finds a redundant link, it uses an algorithm, known as the sta spanningtree algorithm. Rootthe port given this role is the selected best path to reach the root switch. The intended audience of this document is the network architect, system engineer, or network. Spanningtree bpduguard is one of the features that helps you protect your spanning tree topology.
This command shows only the interfaces that are active on the cisco switch. With iosbased switches you can check what version you are running with the command show spanning tree summary. Understanding and configuring spanning tree protocol stp. All, checking in with a request for feedback regarding use of the spanning tree linktype pointtopoint command and its uses.
The spanning tree protocols recommended in the data center design are 802. Also called common spanning tree cst, it assumed one spanning tree instance for the entire bridged network, regardless of the number of vlans. Learn how to configure the spanning tree protocol on cisco switches. To keep up with the speed of these routing protocols another flavor of spanningtree was createdrapid spanningtree. In this example, distribution1 is chosen as the mst0 root, so distribution1 becomes the. I found show spanning tree commands works on cisco 7600 router. Spanning tree path cost value and how is spanning tree. Cisco ccna spanning tree protocol stp spanning tree protocols stps main task is to stop network loops from occurring on your layer2 network bridges or switches. My understanding is that spanning tree is needed on switches to avoid loops. The main purpose of stp is to ensure that you do not create loops when you have redundant paths in your network.
A number of cisco ios command parameters are associated with the show spanningtree command. Introduction to spanningtree spanning tree is a protocol that runs on our switches that helps us to solve loops. For example, if all devices in a network have the bridge priority for vlan 100 set to the default value of 32768, entering the spanningtree vlan. Cisco developed, implemented and published the pervlan spanning tree pvst proprietary protocol using its own.
In my topology above we have a perfectly working spanning tree topology. Configure spanning tree from hp to cisco hardware server. Spanning tree protocol stp ensures a loopfree topology in a local area network lan made up of switches. Hi, i recently ran into this configuration on a cisco 6509 and i read that you are not supposed to enable spanning tree if you create a interface portchannel. For example, by blocking port fa00 of swa, no data traffic is sent on this link and the loop in the network is eliminated. Spanning tree interoperability between hp and cisco switches. On each switch, display the spanning tree table with the show spanning tree command. Uses bridge protocol data unit bpdu version 2 which is backward compatible with the 802. It is recommended that you set the mst0 root manually. Lan switching configuration guide spanning tree protocol cisco. Routing protocols like ospf and eigrp are much faster than spanningtree when they have to deal with changes in the network. Bpdus are sent and processed normally but if a switch suddenly sends a bpdu with a superior bridge id you wont accept it as the root bridge. For example, the id of a bridge with priority 32768 and mac 0200. The varieties of spanningtree protocols include the following.
Spanning tree protocol explained step by step youtube. Stp spanning tree protocol explained with examples. It is desirable to have redundant links in a switched lan so that a single link failure cannot interrupt normal operation of. There is only one active path for each spanning tree. A console cable that is suitable for the supervisor engine in the switch. To enable spanning tree, connect to your switch and type spanning tree mode while in global configuration mode. In this example, distribution1 is chosen as the mst0 root, so distribution1 becomes the cist root. The basic function of stp is to prevent bridge loops and the broadcast radiation that results from them. Rapid spanning tree protocol rstp is the second stp type. Vrrp is configured on the hp 8200zl switches in the core. 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.
Rapid spanningtree is not a revolution of the original spanningtree but an evolution. The following table lists some of the differences among the. Cisco networking allinone for dummies add to cart amazon. Spanning tree follows a strict set of rules which when learnt, will allow you to answer any stp questions you get. 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 protocolsome links below may open a new browser window to display the document you selected. For the sake of this example, the main switch that is being used in the. It is quite useful and should be enabled on the switch interfaces. Dell emc networking and cisco spanning tree interoperability. It is desirable to have redundant links in a switched lan so that a single link failure cannot interrupt normal operation of the network. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology. Spanning tree protocol stp is a layer 2 protocol that runs on bridges and switches. First, it prevents problems caused by loops on a network.
Dell networking and cisco spanning tree interoperability. The spanning tree protocol stp is a network protocol that builds a loopfree logical topology for ethernet networks. Spanning tree protocol stp was developed before switches were created in order. This example shows how the configuration changes when a switch becomes a spanning tree root. Rstp bypass the blocking state and listenning state of stp, and provide forwarding state in 15 seconds. Spanning tree shuts down ports that are in a port fastoperational state if any bpdu is received on them. Rapid spanningtree configuration in a previous lesson i explained the differences between classic and rapid spanning tree and how rapid spanning tree works. In this case, spanning tree protocol will choose the local port which recieves the bpdu with lowest spanning tree port priority value from the neighbour switch as the root port.
If you havent seen it before, i would recommend to look at it first before diving in the configuration. For an ethernet network to function properly, only one active path can exist between two devices. Catalyst 4500 series switch software configuration. Root selection varies depending on the bid of each switch in your lab resulting in varying outputs.
This is a configurable value between 0 to 61440 but the value has to be in increments of 4096. In a valid configuration, port fastenabled ports do not receive bpdus. For example, if the idlefree interfaces are closed by the system administrator, you will be able to view only the active interfaces with this command. There for the best path to reach the switch 1 root switch from switch 4 is via right path because of lowest cost and the port in switch 4 connected to the right path is selected as. The default bridge priority of a cisco switch is 32768. For configuration samples, when and where is the command used and is it possible to see it only at one end of a switch to switch link without issue.
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. Cisco config snippet spanning tree mode pvst spanning tree extend systemid spanning tree vlan 1,1012 priority 0. Spanningtree rootguard rootguard will make sure you dont accept a certain switch as a root bridge. So weve seen a few now in the cisco curriculum, 802.
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