Chapter 10 Spanning Tree Protocol
VES-1616F-3x Series User’s Guide
102
On each bridge, the root port is the port through which this bridge communicates with the root.
It is the port on this switch with the lowest path cost to the root (the root path cost). If there is
no root port, then this switch has been accepted as the root bridge of the spanning tree
network.
For each LAN segment, a designated bridge is selected. This bridge has the lowest cost to the
root among the bridges connected to the LAN.
10.1.2 How STP Works
After a bridge determines the lowest cost-spanning tree with STP, it enables the root port and
the ports that are the designated ports for connected LANs, and disables all other ports that
participate in STP. Network packets are therefore only forwarded between enabled ports,
eliminating any possible network loops.
STP-aware switches exchange Bridge Protocol Data Units (BPDUs) periodically. When the
bridged LAN topology changes, a new spanning tree is constructed.
Once a stable network topology has been established, all bridges listen for Hello BPDUs
(Bridge Protocol Data Units) transmitted from the root bridge. If a bridge does not get a Hello
BPDU after a predefined interval (Max Age), the bridge assumes that the link to the root
bridge is down. This bridge then initiates negotiations with other bridges to reconfigure the
network to re-establish a valid network topology.
10.1.3 STP Port States
STP assigns five port states to eliminate packet looping. A bridge port is not allowed to go
directly from blocking state to forwarding state so as to eliminate transient loops.
Path
Cost
100Mbps
19
10 to 60
1 to 65535
Path
Cost
1Gbps
4
3 to 10
1 to 65535
Path
Cost
10Gbps
2
1 to 5
1 to 65535
Table 24
STP Path Costs
LINK
SPEED
RECOMMENDED
VALUE
RECOMMENDED
RANGE
ALLOWED
RANGE
Table 25
STP Port States
PORT STATE DESCRIPTION
Disabled
STP is disabled (default).
Blocking
Only configuration and management BPDUs are received and processed.
Listening
All BPDUs are received and processed.
Learning
All BPDUs are received and processed. Information frames are submitted to the
learning process but not forwarded.
Forwarding
All BPDUs are received and processed. All information frames are received and
forwarded.
Summary of Contents for VDSL SWITCH VES-1616F-3X
Page 1: ...www zyxel com VES 1616F 3x Series VDSL Switch User s Guide Version 3 60 5 2007 Edition 2 ...
Page 2: ......
Page 7: ...Safety Warnings VES 1616F 3x Series User s Guide 7 ...
Page 8: ...Safety Warnings VES 1616F 3x Series User s Guide 8 ...
Page 28: ...List of Tables VES 1616F 3x Series User s Guide 28 ...
Page 30: ...30 ...
Page 34: ...Chapter 1 Getting to Know Your Switch VES 1616F 3x Series User s Guide 34 ...
Page 42: ...Chapter 3 Hardware Overview VES 1616F 3x Series User s Guide 42 ...
Page 44: ...44 ...
Page 62: ...Chapter 5 System Status and Port Statistics VES 1616F 3x Series User s Guide 62 ...
Page 84: ...Chapter 6 Basic Setting VES 1616F 3x Series User s Guide 84 ...
Page 86: ...86 ...
Page 106: ...Chapter 10 Spanning Tree Protocol VES 1616F 3x Series User s Guide 106 ...
Page 120: ...Chapter 15 Port Authentication VES 1616F 3x Series User s Guide 120 ...
Page 126: ...Chapter 17 Queuing Method VES 1616F 3x Series User s Guide 126 ...
Page 131: ...Chapter 18 Classifier VES 1616F 3x Series User s Guide 131 Figure 51 Classifier Example ...
Page 132: ...Chapter 18 Classifier VES 1616F 3x Series User s Guide 132 ...
Page 138: ...Chapter 19 Policy VES 1616F 3x Series User s Guide 138 Figure 53 Policy Example ...
Page 144: ...Chapter 20 VLAN Stacking VES 1616F 3x Series User s Guide 144 ...
Page 156: ...Chapter 21 Multicast VES 1616F 3x Series User s Guide 156 ...
Page 160: ...Chapter 22 Differentiated Services VES 1616F 3x Series User s Guide 160 ...
Page 161: ...161 PART IV Routing Protocol Static Route 163 DHCP Relay 165 ...
Page 162: ...162 ...
Page 168: ...168 ...
Page 178: ...Chapter 25 Maintenance VES 1616F 3x Series User s Guide 178 ...
Page 192: ...Chapter 27 Diagnostic VES 1616F 3x Series User s Guide 192 ...
Page 196: ...Chapter 28 Syslog VES 1616F 3x Series User s Guide 196 ...
Page 202: ...Chapter 29 Cluster Management VES 1616F 3x Series User s Guide 202 ...
Page 208: ...208 ...
Page 242: ...Chapter 32 Introducing the Commands VES 1616F 3x Series User s Guide 242 ...
Page 266: ...Chapter 34 IEEE 802 1Q Tagged VLAN Commands VES 1616F 3x Series User s Guide 266 ...
Page 274: ...Chapter 35 Troubleshooting VES 1616F 3x Series User s Guide 274 ...
Page 282: ...Chapter 36 Product Specifications VES 1616F 3x Series User s Guide 282 ...
Page 284: ...284 ...
Page 298: ...Appendix B Legal Information VES 1616F 3x Series User s Guide 298 ...