Dell PowerConnect B-FCXs, Руководство по настройке

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212 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
Configuring standard STP parameters
8
Changing STP port parameters
To change the path and priority costs for a port, enter commands such as the following.
PowerConnect(config)#vlan 10
PowerConnect(config-vlan-10)#spanning-tree ethernet 5 path-cost 15 priority 64
Syntax: spanning-tree ethernet < port> path-cost <value> | priority <value> | disable | enable
Specify the <port> variable in the following formats:
•
PowerConnect B-Series FCX stackable switches – <stack-unit/slotnum/portnum>
The path-cost <value> parameter specifies the port cost as a path to the spanning tree root bridge.
STP prefers the path with the lowest cost. You can specify a value from 0 – 65535.
The default depends on the port type:
•
10 Mbps – 100
•
100 Mbps – 19
•
Gbps – 4
•
10 Gbps – 2
•
The priority <value> parameter specifies the preference that STP gives this port relative to
other ports for forwarding traffic out of the spanning tree. You can specify a value from 0 –
240, in increments of 16. If you enter a value that is not divisible by 16, the software returns an
error message. The default value is 128. A higher numerical value means a lower priority;
thus, the highest priority is 0.
•
If you are upgrading a device that has a configuration saved under an earlier software release,
and the configuration contains a value from 0 – 7 for a port STP priority, the software changes
the priority to the default when you save the configuration while running the new release.
The disable | enable parameter disables or re-enables STP on the port. The STP state change
affects only this VLAN. The port STP state in other VLANs is not changed.
STP protection enhancement
STP protection provides the ability to prohibit an end station from initiating or participating in an
STP topology change.
The 802.1W Spanning Tree Protocol (STP) detects and eliminates logical loops in a redundant
network by selectively blocking some data paths (ports) and allowing only the best data paths to
forward traffic.
In an STP environment, switches, end stations, and other Layer 2 devices use Bridge Protocol Data
Units (BPDUs) to exchange information that STP will use to determine the best path for data flow.
When a Layer 2 device is powered ON and connected to the network, or when a Layer 2 device goes
down, it sends out an STP BPDU, triggering an STP topology change.
In some instances, it is unnecessary for a connected device, such as an end station, to initiate or
participate in an STP topology change. In this case, you can enable the STP Protection feature on
the Dell PowerConnect port to which the end station is connected. STP Protection disables the
connected device ability to initiate or participate in an STP topology change, by dropping all BPDUs
received from the connected device.