
C
HAPTER
8
| Spanning Tree Algorithm
Overview
– 272 –
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 108: 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 ECS4660-28F
Страница 1: ...Management Guide www edge core com ECS4660 28F Layer 3 Gigabit Ethernet Switch...
Страница 2: ......
Страница 4: ......
Страница 12: ...ABOUT THIS GUIDE 12...
Страница 64: ...CONTENTS 64...
Страница 90: ...TABLES 90...
Страница 92: ...SECTION I Getting Started 92...
Страница 122: ...SECTION II Web Configuration 122 Multicast Routing on page 825...
Страница 148: ...CHAPTER 3 Using the Web Interface Navigating the Web Browser Interface 148...
Страница 224: ...CHAPTER 5 Interface Configuration VLAN Trunking 224 Figure 68 Configuring VLAN Trunking...
Страница 262: ...CHAPTER 6 VLAN Configuration Configuring VLAN Translation 262...
Страница 304: ...CHAPTER 9 Congestion Control Automatic Traffic Control 304...
Страница 340: ...CHAPTER 11 Quality of Service Attaching a Policy Map to a Port 340...
Страница 452: ...CHAPTER 13 Security Measures DHCP Snooping 452...
Страница 740: ...CHAPTER 17 IP Services Configuring the PPPoE Intermediate Agent 740...
Страница 866: ...CHAPTER 21 Multicast Routing Configuring PIMv6 for IPv6 866...
Страница 882: ...CHAPTER 22 Using the Command Line Interface CLI Command Groups 882...
Страница 1024: ...CHAPTER 26 Remote Monitoring Commands 1024...
Страница 1030: ...CHAPTER 27 Flow Sampling Commands 1030...
Страница 1088: ...CHAPTER 28 Authentication Commands PPPoE Intermediate Agent 1088...
Страница 1162: ...CHAPTER 29 General Security Measures Configuring Port based Traffic Segmentation 1162...
Страница 1186: ...CHAPTER 30 Access Control Lists ACL Information 1186...
Страница 1214: ...CHAPTER 31 Interface Commands Transceiver Threshold Configuration 1214...
Страница 1238: ...CHAPTER 33 Port Mirroring Commands RSPAN Mirroring Commands 1238...
Страница 1258: ...CHAPTER 34 Congestion Control Commands Automatic Traffic Control Commands 1258...
Страница 1270: ...CHAPTER 36 UniDirectional Link Detection Commands 1270...
Страница 1276: ...CHAPTER 37 Address Table Commands 1276...
Страница 1336: ...CHAPTER 39 ERPS Commands 1336...
Страница 1386: ...CHAPTER 40 VLAN Commands Configuring Voice VLANs 1386...
Страница 1406: ...CHAPTER 41 Class of Service Commands Priority Commands Layer 3 and 4 1406...
Страница 1424: ...CHAPTER 42 Quality of Service Commands 1424...
Страница 1536: ...CHAPTER 43 Multicast Filtering Commands MLD Proxy Routing 1536...
Страница 1602: ...CHAPTER 45 CFM Commands Delay Measure Operations 1602...
Страница 1624: ...CHAPTER 47 Domain Name Service Commands 1624...
Страница 1646: ...CHAPTER 48 DHCP Commands DHCP Server 1646...
Страница 1974: ...SECTION IV Appendices 1974...
Страница 1980: ...APPENDIX A Software Specifications Management Information Bases 1980...
Страница 2020: ...ECS4660 28F E102013 ST R03 149100000140A...