User manual

C HAPTER 8 | Spanning Tree Algorithm
Configuring Interface Settings for STA
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ES-2000 Series
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Disabled – Disables the Edge Port setting.
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Auto – The port will be automatically configured as an edge port if
the edge delay time expires without receiving any RSTP BPDU. Note
that edge delay time (802.1D-2004 17.20.4) equals the protocol
migration time if a port's link type is point-to-point (which is 3
seconds as defined in IEEE 802.3D-2004 17.20.4); otherwise it
equals the spanning tree’s maximum age for configuration
messages (see maximum age under "Configuring Global Settings
for STA" on page 108).
An interface cannot function as an edge port under the following
conditions:
■
If spanning tree mode is set to STP (page 108), edge-port mode
cannot automatically transition to operational edge-port state using
the automatic setting.
■
If an interface is in forwarding state and its role changes, the
interface cannot continue to function as an edge port even if the
edge delay time has expired.
■
If the port does not receive any BPDUs after the edge delay timer
expires, its role changes to designated port and it immediately
enters forwarding state (see "Displaying Interface Settings for STA"
on page 116).
◆ Spanning Tree – Enables/disables STA on this interface.
(Default: Enabled)
◆ Priority – Defines the priority used for this port in the Spanning Tree
Protocol. If the path cost for all ports on a switch are the same, the port
with the highest priority (i.e., lowest value) will be configured as an
active link in the Spanning Tree. This makes a port with higher priority
less likely to be blocked if the Spanning Tree Protocol is detecting
network loops. Where more than one port is assigned the highest
priority, the port with lowest numeric identifier will be enabled.
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Default: 128
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Range: 0-240, in steps of 16
◆ Admin Path Cost – This parameter is used by the STA 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. Note that path cost takes precedence over
port priority. (Range: 0 for auto-configuration, 1-65535 for the short
path cost method
2
, 1-200,000,000 for the long path cost method)
By default, the system automatically detects the speed and duplex
mode used on each port, and configures the path cost according to the
values shown below. Path cost “0” is used to indicate auto-configuration
mode. When the short path cost method is selected and the default
2. Refer to "Configuring Global Settings for STA" on page 108 for information on setting
the path cost method.