C
HAPTER
8
| Spanning Tree Algorithm
Overview
– 214 –
lowest cost spanning tree, it enables all root ports and designated ports,
and disables all other ports. Network packets are therefore only forwarded
between root ports and designated ports, eliminating any possible network
loops.
Figure 87: STP Root Ports and Designated Ports
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 (Maximum
Age), the bridge assumes that the link to the Root Bridge is down. This
bridge will then initiate negotiations with other bridges to reconfigure the
network to reestablish a valid network topology.
RSTP
– RSTP is designed as a general replacement for the slower, legacy
STP. RSTP is also incorporated into MSTP. RSTP achieves much faster
reconfiguration (i.e., around 1 to 3 seconds, compared to 30 seconds or
more for STP) by reducing the number of state changes before active ports
start learning, predefining an alternate route that can be used when a node
or port fails, and retaining the forwarding database for ports insensitive to
changes in the tree structure when reconfiguration occurs.
MSTP
– When using STP or RSTP, it may be difficult to maintain a stable
path between all VLAN members. Frequent changes in the tree structure
can easily isolate some of the group members. MSTP (which is based on
RSTP for fast convergence) is designed to support independent spanning
trees based on VLAN groups. Using multiple spanning trees can provide
multiple forwarding paths and enable load balancing. One or more VLANs
can be grouped into a Multiple Spanning Tree Instance (MSTI). MSTP builds
a separate Multiple Spanning Tree (MST) for each instance to maintain
connectivity among each of the assigned VLAN groups. MSTP then builds a
Internal Spanning Tree (IST) for the Region containing all commonly
configured MSTP bridges.
x
Designated
Root
Designated
Port
Designated
Bridge
x
x
x
Root
Port
x
Содержание DG-GS4826S
Страница 2: ...DG GS4826S DG GS4850S E012011 R01 F1 2 2 0 ...
Страница 4: ......
Страница 6: ...ABOUT THIS GUIDE 6 ...
Страница 60: ...SECTION I Getting Started 60 ...
Страница 72: ...CHAPTER 1 Introduction System Defaults 72 ...
Страница 90: ...CHAPTER 2 Initial Switch Configuration Managing System Files 90 ...
Страница 92: ...SECTION II Web Configuration 92 u Unicast Routing on page 539 u Multicast Routing on page 595 ...
Страница 137: ...CHAPTER 4 Basic Management Tasks Resetting the System 137 Figure 23 Restarting the Switch Regularly ...
Страница 138: ...CHAPTER 4 Basic Management Tasks Resetting the System 138 ...
Страница 204: ...CHAPTER 6 VLAN Configuration Configuring MAC based VLANs 204 ...
Страница 212: ...CHAPTER 7 Address Table Settings Clearing the Dynamic Address Table 212 ...
Страница 238: ...CHAPTER 9 Rate Limit Configuration 238 Figure 106 Configuring Rate Limits ...
Страница 268: ...CHAPTER 12 Quality of Service Attaching a Policy Map to a Port 268 ...
Страница 368: ...CHAPTER 14 Security Measures DHCP Snooping 368 ...
Страница 422: ...CHAPTER 15 Basic Administration Protocols Remote Monitoring 422 ...
Страница 466: ...CHAPTER 16 Multicast Filtering Multicast VLAN Registration 466 Figure 273 Showing All MVR Groups Assigned to a Port ...
Страница 487: ...CHAPTER 17 IP Configuration Setting the Switch s IP Address IP Version 6 487 Figure 285 Showing Reported MTU Values ...
Страница 488: ...CHAPTER 17 IP Configuration Setting the Switch s IP Address IP Version 6 488 ...
Страница 538: ...CHAPTER 20 IP Services Forwarding UDP Service Requests 538 ...
Страница 594: ...CHAPTER 21 Unicast Routing Configuring the Open Shortest Path First Protocol Version 2 594 ...
Страница 624: ...CHAPTER 22 Multicast Routing Configuring PIMv6 for IPv6 624 ...
Страница 638: ...CHAPTER 23 Using the Command Line Interface CLI Command Groups 638 ...
Страница 712: ...CHAPTER 26 SNMP Commands 712 ...
Страница 720: ...CHAPTER 27 Remote Monitoring Commands 720 ...
Страница 776: ...CHAPTER 29 Authentication Commands Management IP Filter 776 ...
Страница 876: ...CHAPTER 34 Port Mirroring Commands Local Port Mirroring Commands 876 ...
Страница 898: ...CHAPTER 37 Address Table Commands 898 ...
Страница 998: ...CHAPTER 41 Quality of Service Commands 998 ...
Страница 1060: ...CHAPTER 42 Multicast Filtering Commands MLD Proxy Routing 1060 ...
Страница 1078: ...CHAPTER 43 LLDP Commands 1078 ...
Страница 1088: ...CHAPTER 44 Domain Name Service Commands 1088 ...
Страница 1164: ...CHAPTER 47 IP Interface Commands IPv6 to IPv4 Tunnels 1164 ...
Страница 1260: ...CHAPTER 48 IP Routing Commands Open Shortest Path First OSPFv3 1260 ...
Страница 1304: ...SECTION IV Appendices 1304 ...
Страница 1310: ...APPENDIX A Software Specifications Management Information Bases 1310 ...
Страница 1343: ...DG GS4826S DG GS4850S E012011 R02 F1 2 2 0 ...
Страница 1344: ......