User's Manual

C HAPTER 4 | Configuring the Switch
Configuring the Spanning Tree Algorithm
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PARAMETERS
These parameters are displayed:
Basic Settings
◆ Protocol Version – Specifies the type of spanning tree used on this
switch. (Options: STP, RSTP, MSTP; Default: MSTP)
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STP: Spanning Tree Protocol (IEEE 802.1D); i.e., the switch will use
RSTP set to STP forced compatibility mode.
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RSTP: Rapid Spanning Tree (IEEE 802.1w)
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MSTP: Multiple Spanning Tree (IEEE 802.1s); This is the default.
◆ Bridge Priority – Bridge priority is used in selecting the root device,
root port, and designated port. The device with the highest priority
becomes the STA root device. However, if all devices have the same
priority, the device with the lowest MAC address will then become the
root device. (Note that lower numeric values indicate higher priority.)
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Default: 128
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Range: 0-240, in steps of 16
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Options: 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192,
208, 224, 240
◆ Forward Delay – The maximum time (in seconds) this device will wait
before changing states (i.e., discarding to learning to forwarding). This
delay is required because every device must receive information about
topology changes before it starts to forward frames. In addition, each
port needs time to listen for conflicting information that would make it
return to a discarding state; otherwise, temporary data loops might
result.
Minimum: The higher of 4 or [(Max. Message Age / 2) + 1]
Maximum: 30
Default: 15
◆ Max Age – The maximum time (in seconds) a device can wait without
receiving a configuration message before attempting to reconfigure. All
device ports (except for designated ports) should receive configuration
messages at regular intervals. Any port that ages out STA information
(provided in the last configuration message) becomes the designated
port for the attached LAN. If it is a root port, a new root port is selected
from among the device ports attached to the network. (Note that
references to “ports” in this section mean “interfaces,” which includes
both ports and trunks.)
Minimum: The higher of 6 or [2 x (Hello Time + 1)]
Maximum: The lower of 40 or [2 x (Forward Delay - 1)]
Default: 20
◆ Max Hop Count – The maximum number of hops allowed in the MST
region before a BPDU is discarded. (Range: 6-40; Default: 20)