Extreme Networks ExtremeWare 7.3.0, Справочник по командам

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ExtremeWare Software 7.3.0 Command Reference Guide 1003
13
STP Commands
This chapter describes:
• Commands related to creating, configuring, enabling, and disabling Spanning Tree Protocol (STP) on
the switch
• Commands related to enabling and disabling Rapid Spanning Tree Protocol (RSTP) on the switch
• Commands related to displaying and resetting STP settings on the switch
The Spanning Tree Protocol (STP) is a bridge-based mechanism for providing fault tolerance on
networks. STP is a part of the 802.1d bridge specification defined by the IEEE Computer Society. To
explain STP in terms used by the 802.1d specification, the switch will be referred to as a bridge.
STP allows you to implement parallel paths for network traffic, and ensure that:
• Redundant paths are disabled when the main paths are operational.
• A redundant path is enabled if the main path fails.
The Rapid Spanning Tree Protocol (RSTP; 802.1w) provides an enhanced spanning tree algorithm that
improves the convergence speed of bridged networks. RSTP takes advantage of point-to-point links in
the network and actively confirms that a port can safely transition to the forwarding state without
relying on any timer configurations. If a network topology change or failure occurs, RSTP rapidly
recovers network connectivity by confirming the change locally before propagating that change to other
devices across the network. For broadcast links, there is no difference in convergence time between STP
and RSTP.
RSTP supersedes legacy STP protocols, supports the existing STP parameters and configurations, and
allows for seamless interoperability with legacy STP.
Spanning Tree Domains
The switch can be partitioned into multiple virtual bridges. Each virtual bridge can run an independent
Spanning Tree instance. Each Spanning Tree instance is called a
Spanning Tree Domain (STPD). Each
STPD has its own root bridge and active path. After an STPD is created, one or more VLANs can be
assigned to it.
A port can belong to multiple STPDs. In addition, a VLAN can span multiple STPDs.
The key points to remember when configuring VLANs and STP are:
• Each VLAN forms an independent broadcast domain.