STP is the short form for Spanning Tree Protocol & RSTP (Rapid Spanning shed some light on the differences between PVST and RPVST?. and fault-tolerance. STP, RSTP, PVST, and MST are all spanning tree protocols w What’s the difference between MSTP and OTN? Views · Are STP. To prevent loop between switches, Cisco uses Spanning-Tree protocol. STP is the The only difference here is using in Vlan instead of STP. The delay in.

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Understanding Spanning Tree Protocols – STP, RSTP, MSTP –

When there are two or more paths to the same destination, there is a danger of broadcast packets getting in to an infinite loop and hence causing congestion in the network. As it shown in below code, we have different instances and in each instance we have Vlans.

PortFast causes a switch or trunk port to enter the spanning tree forwarding state immediately, bypassing the listening and learning states.

The port prepares to participate in frame forwarding and begins to populate the MAC address table. RSTP does not have a blocking port state. BPDUs are used as a keepalive mechanism.

Therefore, three consecutively missed BPDUs indicate lost connectivity between a bridge and its neighboring root or designated bridge. Excellent explanation to new learners in most easiest way and more importantly simple language. They establish the best path least cost connections to the root switch with the help of BPDU messages obtained from other switches. This provides for both link redundancy and switch redundancy in the network.


This is problematic only if a large number of VLANs are configured. Then, we have selection between switch B and C, as we mentioned, switch B has the lowest Mac-Address, so it becomes Designated port and in switch C connection will be blocked.

Connect to Cisco devices. This design allows the spanning tree to be optimized for the traffic of each VLAN. Default priority of switch is and is multiple of between while, default port-priority in switch is and multiple of STP has determined that the port can participate in frame forwarding according to the BPDU frames that the switch has received. Dear Rajesh, as usual a very nice article.

The msp port is selected on the switch that has the lowest-cost path to the root bridge. RSTP is able to actively confirm that a port can safely transition to the forwarding state without having to rely on a timer configuration.

The loop guard feature makes additional checks. However, because there is only one root bridge, traffic for all VLANs flows over the same path, which can lead to suboptimal traffic flows.

Note that the number of ports in each of the various states blocking, listening, learning, or forwarding can be displayed with the show spanning-tree summary command. It prevents creating a loop by forwarding some VLANs on another trunk.

Non-edge ports are categorized into two link types: If it is not selected manually, the switches will themselves elect a root switch. Configuring an edge port to be attached to another switch is not recommended. If the root switch fails, all the other switches repeat the election process and select a new root switch, from the available switches.


Discarding — wherein a port discards information received on the interface, discards frames switched from another interface for forwarding, does not learn MAC addresses, and listens for BPDUs.

Understanding Spanning Tree Protocols – STP, RSTP, MSTP

Root ports are able to make a rapid transition to the forwarding state as soon as the port is in sync that is, receives a BPDU from the root bridge. Alternate ports normally remain in the blocking state to logically break the loop topology. The only difference here is using in Vlan instead of STP. The fast aging of the information allows failures to be detected quickly.

Difference Between RSTP and PVST

Chapter Description Network redundancy is a key to maintaining network reliability. The other switches in the network are called designated switches. Figure shows a network running RSTP. When a port is in the blocking state, it does not forward traffic, but it can still process received Divference messages.

Types of Spanning Tree Protocols 3. MST allows you to build multiple spanning trees over trunks. The spanning diffreence is determined through the information learned by the exchange of the BPDU frames between the interconnected switches. Its possible and recommended to manually select the root switch.

It selects the designated port on each segment. Trunk Port Tag Port. The Root Switch is the Central reference Switch. This is the same idea of STP.