Sơ đồ hình tròn stp có bao nhiêu root port năm 2024
Spanning tree protocol (STP) (IEEE 802.1D) is predominantly used to prevent layer 2 loops and broadcast storms and is also used for network redundancy. It was developed around the time where recovery from an outage that took upwards of a minute or more was acceptable. Throughout the years, as technology improved and critical applications relied on stable connections, businesses moved away from these long recovery times and looked for faster solutions. Show STP evolved into rapid spanning tree protocol (RSTP) (802.1w), which offers several improvements over STP (802.1D). It has new port states and port roles and, more importantly, faster convergence times. Both STP or RSTP are critical to having a healthy network and an administrator would benefit from using RSTP over STP. RSTP is the answer for businesses that require faster recovery times. This document provides an overview of the STP and RSTP standards. You will learn about the following:
STPSwitches within the same network need to be enabled for STP before they run the spanning tree algorithm so they can accurately determine which switch should be elected the “root bridge.” This designated root bridge will be responsible for sending configuration bridge protocol data units (BPDUs) along with other information to its directly connected switches that, in turn, forward the BPDUs to their neighboring switches. Each switch has a bridge ID priority value (BID), which is a combination of a priority value (default 32768) and the switch’s own MAC address. The switch with the lowest BID will become the root bridge. STP Port StatesThere are five STP switchport states; these are:
STP Port Roles
STP Election ProcessWhen switches are first turned on, they will send configuration BPDUs containing their BIDs, with each switch initially believing themselves to be the root bridge. However, when a switch receives a BPDU with a superior (lower value) BID, that switch will stop originating configuration BPDUs and will instead relay these superior BPDUs to its neighboring switches. Once a root bridge has finally been announced, a second election process begins to determine the “root port” selection process (the port on a switch that will forward frames to the root bridge). This process will follow the steps below until a root port is elected:
Election Process DiagramLet’s follow the process for Switch 2 in the diagram below.
Rapid Spanning Tree Protocol (RSTP)Rapid spanning tree protocol (RSTP) is as its name suggests, a faster transition to a port-forwarding state. Unlike STP, which has five switchport states, RSTP has only three: discarding, learning, and forwarding. RSTP Port States
RSTP Port Roles
Alternate and Backup PortsIn RSTP, the election process is the same as STP, except the blocked port is split into two new port roles: alternate and backup. AlternateAn alternate port receives BPDUs from another switch but remains in a blocked state. For example, let’s say a switch has two paths to the root bridge. It will elect one of the two ports as a root port and the other will become an alternate port. If at any time the root port fails, this redundant path—the alternate port—will become the new root port. BackupA backup port receives BPDUs from its own switch but remains in a blocked state. For example, If a switch has two ports connecting to different switches, then one port will be elected as a root port and the other will become the backup port. |