ZyXEL Communications ES-4024A - Manual (Page 67)

ES-4024A Series Switch Support Notes
All contents copyright (c) 2006 ZyXEL Communications Corporation.
67
To ring a network by building reducdent 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 bridges
and 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.
1. When Host sends a broadcast frame, like an ARP request to Router,
the frame will be received by Switch A.
2. Switch A identify the destination MAC address field (broadcast
FF:FF:FF:FF:FF:FF) in the frame and determine to flood it onto
Segment B.
3. When the broadcast frame arrives at Switch B, Switch will repeat
above process, flood it to Segment A.
4. The broadcast frame will endlessly travel around the loop network
even Router has already received this frame.