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C
HAPTER
9: S
PANNING
T
REE
P
ROTOCOL
What is STP?
Using the Spanning Tree Protocol (STP) makes your network more
resilient to link failure and also provides a protection from loops — one
of the major causes of broadcast storms.
STP is a bridge-based system that allows you to implement parallel paths
for network traffic and uses a loop-detection process to:
■
Find and disable the less efficient paths (that is, the paths that have a
lower bandwidth).
■
Enable one of the less efficient paths if the most efficient path fails.
As an example,
Figure 45
shows a network containing three LAN
segments separated by three bridges. With this configuration, each
segment can communicate with the others using two paths. Without STP,
this configuration creates loops that cause the network to overload;
however, STP allows you to have this configuration because it detects
duplicate paths and prevents, or
blocks
, one of them from forwarding
traffic.
Figure 46
shows the result of enabling STP on the bridges in the
configuration. The STP system has decided that traffic from LAN segment
2 to LAN segment 1 can only flow through Bridges C and A.
If the link through Bridge C fails, as shown in
Figure 47
, the STP process
reconfigures the network so that traffic from segment 2 flows through
Bridge B.
Figure 45
A network configuration that creates loops
Summary of Contents for SuperStack II
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Page 154: ...154 CHAPTER 4 WORKING WITH THE COMMAND LINE INTERFACE ...
Page 156: ......
Page 162: ...162 CHAPTER 5 PORT TRUNKS ...
Page 169: ...VLANs and Your Switch 169 Figure 32 Forwarding unknown 802 1Q tags ...
Page 173: ...VLAN Configuration for Beginners 173 Figure 34 Simple example Untagged connections using hubs ...
Page 180: ...180 CHAPTER 6 VIRTUAL LANS VLANS ...
Page 188: ...188 CHAPTER 7 FASTIP ...
Page 200: ...200 CHAPTER 9 SPANNING TREE PROTOCOL Figure 49 STP configurations ...
Page 210: ...210 CHAPTER 10 RMON ...
Page 211: ...IV PROBLEM SOLVING Chapter 11 Problem Solving ...
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Page 224: ...224 CHAPTER 11 PROBLEM SOLVING ...
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