C
HAPTER
8
| Spanning Tree Algorithm
Configuring Interface Settings for STA
– 217 –
However, remember that Edge Port should only be enabled for ports
connected to an end-node device. (Default: Enabled)
■
Enabled – Manually configures a port as an Edge Port.
■
Disabled – Disables the Edge Port setting.
■
Auto – The port will be automatically configured as an edge port if
the edge delay time expires without receiving any RSTP or MSTP
BPDUs. 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 209).
An interface cannot function as an edge port under the following
conditions:
■
If spanning tree mode is set to STP (page 209), edge-port mode
cannot automatically transition to operational edge-port state using
the automatic setting.
■
If loopback detection is enabled (page 208) and a loopback BPDU is
detected, the interface cannot function as an edge port until the
loopback state is released.
■
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 220).
◆ 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.
■
Default: 128
■
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
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