Installation manual

3-158
SIGNAMAX LLC • www.signamax.eu
An MST Region consists of a group of interconnected bridges that have the same MST
Configuration Identifiers (including the Region Name, Revision Level and Configuration
Digest – see “Configuring Multiple Spanning Trees” on page 3-171). An MST Region may
contain multiple MSTP Instances. An Internal Spanning Tree (IST) is used to connect all
the MSTP switches within an MST region. A Common Spanning Tree (CST) interconnects
all adjacent MST Regions, and acts as a virtual bridge node for communications with STP
or RSTP nodes in the global network.
MSTP connects all bridges and LAN segments with a single Common and Internal
Spanning Tree (CIST). The CIST is formed as a result of the running spanning tree
algorithm between switches that support the STP, RSTP, MSTP protocols.
Displaying Global Settings
You can display a summary of the current bridge STA information that applies to the entire
switch using the STA Information screen.
Field Attributes
• Spanning Tree State – Shows if the switch is enabled to participate in an
STA-compliant network.
• Bridge ID – A unique identifier for this bridge, consisting of the bridge priority, the MST
Instance ID 0 for the Common Spanning Tree when spanning tree mode is set to MSTP
(page 3-161), and MAC address (where the address is taken from the switch system).
• Max Age – The maximum time (in seconds) a device can wait without receiving a
configuration message before attempting to reconfigure. All device ports (except for
designated ports) should receive configuration messages at regular intervals. Any port
that ages out STA information (provided in the last configuration message) becomes the
designated port for the attached LAN. If it is a root port, a new root port is selected from
among the device ports attached to the network. (References to “ports” in this section
mean “interfaces,” which includes both ports and trunks.)
• Hello Time – Interval (in seconds) at which the root device transmits a configuration
message.
• Forward Delay – The maximum time (in seconds) the root device will wait before
changing states (i.e., discarding to learning to forwarding). This delay is required