ZyXEL Communications VES-1616 manual Ringing a network by building redundant, Broadcast storm

ZyXEL VES-1616/24FA-5x Series Support Notes

Ringing a network by building redundant

links and connections between Switch

What is Spanning Tree Protocol?

Spanning Tree Overview

Spanning-Tree Protocol (STP) is a Layer 2 protocol designed to run on the bridges and the switches. The specification for STP is defined in IEEE 802.1d. The main purpose of STP is to ensure that you do not run into a loop situation when you have redundant paths in your network. STP detects/disables network loops and provides backup links between switches or bridges. It allows the device to interact with other STP compliant devices in your network to ensure that only one path exists between any two stations on the network.

The redundant topology without STP will cause the following problem:

1. Broadcast storm:

Without Spanning Tree loop avoidance mechanism, each switch will endlessly flood broadcast packets to all ports. This situation is called broadcast storm.

zWhen Host sends a broadcast frame, like an ARP request to Router, the frame will be received by Switch A.

zSwitch A identifies the destination MAC address field (broadcast FF:FF:FF:FF:FF:FF) in the frame and determine to flood it onto Segment B.

zWhen the broadcast frame arrives at Switch B, the switch will repeat above process, flood it to Segment A.

zThe broadcast frame will endlessly travel around the loop network even id the router has already received this frame.

All contents copyright 2008 ZyXEL Communications Corporation. 91