Allied Telesis Rapier i AT-RP16Fi/SC, Руководство пользователя

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Layer 2 Switching 97
Software Release 2.6.1
C613-02025-00 REV C
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
so that a port operating at 10Mbps has a default pathcost of 100, a port
operating at 100 Mbps has a default pathcost of 10, and a port operating at 1
Gbps has a default pathcost of 1. Setting the pathcost to a larger value on a
particular port is likely to reduce the traffic over the LAN connected to it. This
may be appropriate if the LAN has lower bandwidth, or if there are reasons for
limiting the traffic across it. To modify the STP port pathcost, use the
command:
SET STP={stp-name|ALL} PORT={port-list|ALL}
PATHCOST=1..1000000
If the PATHCOST of a port has not been explicitly set by the user, or the default
values have been restored to the port, then the default PATHCOST for the port
will vary as the speed of the port varies.
The default value for PATHCOST is set according to the speed. For a port
operating at 100 Mbps, the default value is 19. For a port operating at 10 Mbps,
the default value is 100.
To restore default port pathcost and priority, use the command:
SET STP={stp-name|ALL} PORT={port-list|ALL} DEFAULT
When an STP is enabled in a looped or meshed network, it disables and
enables particular ports belonging to it dynamically, to eliminate redundant
links. All ports in a VLAN belong to the same STP, and their participation in
STP configuration, and hence the possibility of them being elected to the STP’s
active topology is enabled by default. To enable or disable particular ports, use
the commands:
ENABLE STP PORT={ port-list |ALL}
DISABLE STP PORT={ port-list |ALL}
To display STP port information, use the command:
SHOW STP[={ stp-name |ALL}] PORT={ port-list |ALL}