196
C
HAPTER
9: S
PANNING
T
REE
P
ROTOCOL
How STP Works
STP Requirements
Before it can configure the network, the STP system requires the
following:
■
Communication between all the bridges. This communication is
carried out using Bridge Protocol Data Units (BPDUs), which are
transmitted in packets with a known multicast address.
■
Each bridge to have a Bridge Identifier. This specifies which bridge acts
as the central reference point, or Root Bridge, for the STP system —
the lower the Bridge Identifier, the more likely the bridge is to become
the Root Bridge. The Bridge Identifier is calculated using the MAC
address of the bridge and a priority defined for the bridge. The default
priority of your Switch is 32768.
■
Each port to have a cost. This specifies the efficiency of each link,
usually determined by the bandwidth of the link — the higher the
cost, the less efficient the link. Table 9 shows the default port costs for
your Switch.
CAUTION:
If you are using STP on a network that contains various
network devices, ensure that the cost for each port type is the same for
each device. If the costs are different, STP cannot determine the efficiency
of each link accurately. You can change the port costs of devices on your
network using Transcend Network Management software.
Table 9
Default port costs
Port Type
Duplex
Cost
1000BASE-SX
Full
4
Port trunk containing 100BASE-TX/100BASE-FX
Full/Half
15
100BASE-TX/100BASE-FX
Full
Half
18
19
Port trunk containing 10BASE-T only
Full/Half
90
10BASE-T
Full
95
10BASE-T
Half
100
Summary of Contents for SuperStack II
Page 12: ......
Page 18: ......
Page 42: ......
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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