How fast is rapid spanning tree

Port assignments change through messages exchanged throughout the domain. An RSTP device generates configuration messages once per hello time interval. If an RSTP device does not receive a configuration message from its neighbor after an interval of three hello times, it determines that the connection with the neighbor is lost. When a root port or a designated port fails on a device, the device generates a configuration message with the proposal bit set. Once its neighbor device receives this message, it verifies that this configuration message is valid for that port and starts a synchronizing operation to ensure that all of its ports are in sync with the new information.

Join Sign In. Date: Dec 1, Contents Objectives Key Terms Introduction 3. Chapter Description Network redundancy is a key to maintaining network reliability.

Varieties of Spanning Tree Protocols 3. Overview 3. Types of Spanning Tree Protocols 3. Characteristics of the Spanning Tree Protocols 3. This version is slow to converge. This design allows the spanning tree to be optimized for the traffic of each VLAN. Convergence is per-VLAN and is slow, like This version addresses the convergence issues and the suboptimal traffic flow issues. It supports up to 16 instances of RSTP. Table summarizes the STP characteristics.

They are in the original Bits 1 and 6 are used for the proposal agreement process used for rapid convergence. Bits 2 to 5 encode the role and state of the port. Bits 4 and 5 are used to encode the port role using a 2-bit code. Figure Edge Ports. Figure Non-Edge Ports. NOTE Configuring an edge port to be attached to another switch is not recommended. Spanning Tree Configuration 3. Overview Pearson Education, Inc. Collection and Use of Information To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including: Questions and Inquiries For inquiries and questions, we collect the inquiry or question, together with name, contact details email address, phone number and mailing address and any other additional information voluntarily submitted to us through a Contact Us form or an email.

Surveys Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites.

Contests and Drawings Occasionally, we may sponsor a contest or drawing. Newsletters If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information ciscopress. Service Announcements On rare occasions it is necessary to send out a strictly service related announcement.

Customer Service We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form. Other Collection and Use of Information Application and System Logs Pearson automatically collects log data to help ensure the delivery, availability and security of this site.

Web Analytics Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site.

Cookies and Related Technologies This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Security Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children This site is not directed to children under the age of Marketing Pearson may send or direct marketing communications to users, provided that Pearson will not use personal information collected or processed as a K school service provider for the purpose of directed or targeted advertising.

Such marketing is consistent with applicable law and Pearson's legal obligations. Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.

Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn. Sale of Personal Information Pearson does not rent or sell personal information in exchange for any payment of money. Supplemental Privacy Statement for California Residents California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice.

Sharing and Disclosure Pearson may disclose personal information, as follows: As required by law. Links This web site contains links to other sites.

Requests and Contact Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Last Update: November 17, Email Address. About Affiliates Cisco Systems, Inc. The port is an alternate port and does not participate in frame forwarding. Listens for the path to the root. Learns the MAC addresses. The port is considered part of the active topology.

It forwards data frames and sends and receives BPDU frames. Remember the port states of spanning-tree? We have a blocking, listening, learning and forwarding port state. This is the first difference between spanning-tree and rapid spanning-tree. Rapid spanning-tree only has three port states:. You already know about learning and forwarding but discarding is a new port state.

Basically it combines the blocking and listening port state. Do you remember all the other port roles that spanning-tree has? The other switches non-root have to find the shortest cost path to the root bridge.

This is the root port. The next step is to select the designated ports:. The port will become the designated port if it can send the best BPDU. SW1 as a root bridge will always have the best ports so all of interfaces will be designated.

The interfaces that are left will be blocked:. Let me show you a new example with a port state that is new for rapid spanning-tree:. You are very unlikely to see this port on a production network though. The BPDU is different for rapid spanning-tree. In the classic spanning-tree the flags field only had two bits in use:. All bits of the flag field are now used.

The role of the port that originates the BPDU will be added by using the port role field, it has the following options:. Switches running the old version of spanning-tree will drop this new BPDU version.

Forwarding Forwarding The port can send and receive data, learn MAC addresses, and forward data to its destination. These are messages that are exchanged between switches on the network. Designated Port The port selected in each local area network LAN segment which provides the lowest root path cost. The higher the link speed, the lower the cost value. Alternate Port If a port is not to be used as a designated port, it will become an alternate port.

This is a backup for the root port in case of failure and is blocked during typical operation of the root port. Backup Port This is the backup for the designated port. If the root port fails, the backup port becomes the new designated port. The backup port is normally blocked with the designated port is operating correctly. The RSTP algorithm follows these general steps: Determine the root bridge: The switch with the lowest bridge priority will be the root bridge.

If there is a tie, the switch with the lowest MAC address is selected. All interfaces on the root bridge are placed in a Forwarding state: In a forwarding state, the port will send and receive data and learn MAC addresses on the network. All other switches on the network non-root select a root port: The root port is the best path to the root bridge based on its port cost.

The lower the port speed, the higher the cost. Therefore, the fastest port is chosen as the root port based on its low port cost. There is only one root port per non-root switch. Designated ports are selected: These ports are permitted to forward traffic and are also selected based on port cost. All root bridge ports are designated ports. All other ports are in a discarding blocking state: These ports are not passing data to other switches on the network and not updating MAC address tables.

When this bridge is created, it allows the Ethernet ports 1 and 2 to send and receive data.