3Com Network Jack NJ2000
Page 37 of 44
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STA Introduction
The Spanning Tree Algorithm (STA) can be used to detect and disable network loops, and
to provide backup links between switches, bridges or routers. This allows the switch to
interact with other bridging devices (that is, an STA-compliant switch, bridge or router) in
your network to ensure that only one route exists between any two stations on the network,
and provide backup links which automatically take over when a primary link goes down.
The spanning tree algorithms supported by this switch include these versions:
STP Spanning Tree Protocol (IEEE 802.1D)
RSTP Rapid Spanning Tree Protocol (IEEE 802.1w)
RSTP System Configuration
There are five configurable parameters in this table. As follows:
System Priority
- This parameter configures the spanning tree priority globally for
this switch. The device with the highest priority becomes the STA root device.
However, if all devices have the same priority, the device with the lowest MAC
address will then become the root device. Number between 0 - 61440 in increments
of 4096. Therefore, there are 16 distinct values.
Hello Time
- Interval (in seconds) at which the root device transmits a
configuration message (BPDU frame). Number between 1 - 10 (default is 2).
Max Age
- The maximum time (in seconds) a device can wait without receiving a
configuration message before attempting to reconfigure. That also means the
maximum life time for a BPDU frame. Number between 6 - 40 (default is 20).
Forward Delay
- The maximum time (in seconds) the root device will wait before
changing states (i.e., discarding to learning to forwarding). Number between 4 - 30
(default is 15).
Force Version
- Set and show the RSTP protocol to use. Normal - use RSTP,
Compatible - compatible with STP.
RSTP Port Configuration
The table has one row for each port and four columns. The columns are:
Port
- The port ID. It cannot be changed. Aggregations mean any configured trunk
group.
Enabled
- Click on the tick-box to enable/disable the RSTP protocol for the port.
Edge
- Expect the port to be an edge port (linking to an end station) or a link to
another STP device.
Path Cost
- This parameter is used by the STP to determine the best path between
devices. Therefore, lower values should be assigned to ports attached to faster
media, and higher values assigned to ports with slower media. Set the RSTP path
cost on the port. Number between 0 - 200000000. 0 means auto-generated path
cost.
