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92 AT-8800 Series Switch User Guide
Software Release 2.6.1
C613-02039-00 REV A
The various parameters used by the Spanning Tree Algorithm for the specified
ports, or all ports within the specified STP, or all STPs, are set with the SET STP
PORT command:
SET STP={stp-name|ALL} PORT={port-list|ALL}
A port can belong to a single STP. This means that if the port is member of
multiple VLANs then all those VLANs must belong to the same STP.
The STP parameter specifies an STP name. If no parameter is entered, the
default value is ALL.
The PORT parameter specifies a list of ports that can belong to any STP. The
default value is ALL.
Each port has a port priority, with a default value of 128, used to determine
which port should be the root port for the STP if two ports are connected in a
loop. The lower number indicates the higher priority.
SET STP={stp-name|ALL} PORT={port-list|ALL}
PORTPRIORITY=0..255 [other-parameters]
The PORTPRIORITY parameter sets the value of the priority field contained in
the port identifier. The Spanning Tree Algorithm uses the port priority when
determining the root port for each switch. The port with the lowest value is
considered to have the highest priority. The default value is 128. Each STP has
its own independent PORTPRIORITY parameter for each member port.
Each port also has a path cost, which is used if the port is the root port for the
STP on the switch. The path cost is added to the root path cost field in
configuration messages received on the port to determine the total cost of the
path to the root bridge. The default PATHCOST values depend on the port
speed, according to the formula:
PATHCOST = 1000 / Port_Speed_in_MB_per_second
Switch Max Age The value of the Max Age parameter when this switch is the
Root or is attempting to become the Root. This parameter
is set by the MAXAGE parameter in the SET STP command.
Switch Hello Time The value of the Hello Time parameter when this switch is
the Root or is attempting to become the Root. This
parameter is set by the HELLOTIME parameter in the SET
STP command.
Switch Forward Delay The value of the Forward Delay parameter when this switch
is the Root or is attempting to become the Root. This
parameter is set by the FORWARDDELAY parameter in the
SET STP command.
Hold Time The minimum time in seconds between the transmission of
configuration BPDUs through a given LAN Port. The value
of this fixed parameter is 1, as specified in IEEE 802.1d. This
parameter applies only to STP running in standard mode.
Transmission Limit In Rapid mode, this indicates the number of BPDUs that
may be transmitted in the interval specified by Hello Time.
The value of this fixed parameter is 3, as specified in IEEE
802.1t.
Table 18: Parameters in the output of the SHOW STP command (Continued).
Parameter Meaning