
172
C
HAPTER
9: B
RIDGE
-W
IDE
AND
B
RIDGE
P
ORT
P
ARAMETERS
■
Bridges elect as the
designated bridge
on each LAN the bridge with
the
least cost path
to the root bridge. The designated bridge forwards
frames between that LAN and the path to the root bridge. For this
reason, the root bridge is
always
the designated bridge for its
attached LANs. The port through which the designated bridge is
attached to the LAN is elected the
designated port.
■
Bridges choose a
root port
that gives the best path from themselves to
the root bridge.
■
Bridges select ports to include in the STP topology. The ports that are
selected include the root port plus any designated ports. Data traffic is
forwarded to and from ports that have been selected in the STP
topology.
Figure 4 shows a bridged network with its STP elements.
Figure 4
STP Root and Designated Bridges and Ports
(R)
LAN 1
LAN 2
Root bridge
(D)
(D)
(R) = Root port
(D) = Designated port
(B) = Backup port
LAN 3
Bridge
LAN 4
(R)
(B)
Bridge
(D)
(D)
Designated
bridge for
LANs 1, 2, and 4
Designated
bridge for
LAN 3
L2/3
L2/3
L2/3
Содержание 4007
Страница 1: ...http www 3com com Switch 4007 Implementation Guide Release 3 0 5 Part No 10013673 Published May 2000 ...
Страница 36: ...36 ABOUT THIS GUIDE ...
Страница 37: ...I UNDERSTANDING YOUR SWITCH 4007 SYSTEM Chapter 1 Configuration Overview ...
Страница 38: ......
Страница 50: ...50 CHAPTER 1 CONFIGURATION OVERVIEW ...
Страница 52: ......
Страница 70: ...70 CHAPTER 3 INSTALLING MANAGEMENT MODULES ...
Страница 110: ...110 CHAPTER 4 CONFIGURING AND USING EME OPTIONS ...
Страница 130: ...130 CHAPTER 5 MANAGING THE CHASSIS POWER AND TEMPERATURE ...
Страница 222: ...222 CHAPTER 11 IP MULTICAST FILTERING WITH IGMP ...
Страница 240: ...240 CHAPTER 13 RESILIENT LINKS ...
Страница 304: ...304 CHAPTER 14 VIRTUAL LANS VLANS ...
Страница 350: ...350 CHAPTER 15 PACKET FILTERING ...
Страница 506: ...506 CHAPTER 19 OPEN SHORTEST PATH FIRST OSPF ROUTING ...
Страница 534: ...534 CHAPTER 20 IPX ROUTING ...
Страница 612: ...612 CHAPTER 22 QOS AND RSVP ...
Страница 656: ...656 CHAPTER 23 DEVICE MONITORING ...
Страница 657: ...IV REFERENCE Appendix A Technical Support Index ...
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