User manual

C HAPTER 4 | Configuring the Switch
Configuring the Spanning Tree Algorithm
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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)
An MST region is treated as a single node by the STP and RSTP
protocols. Therefore, the message age for BPDUs inside an MST region
is never changed. However, each spanning tree instance within a
region, and the common internal spanning tree (CIST) that connects
these instances use a hop count to specify the maximum number of
bridges that will propagate a BPDU. Each bridge decrements the hop
count by one before passing on the BPDU. When the hop count reaches
zero, the message is dropped.
◆ Transmit Hold Count – The number of BPDU's a bridge port can send
per second. When exceeded, transmission of the next BPDU will be
delayed. (Range: 1-10; Default: 6)
Advanced Settings
◆ Edge Port BPDU Filtering – BPDU filtering allows you to avoid
transmitting BPDUs on configured edge ports that are connected to end
nodes. By default, STA sends BPDUs to all ports regardless of whether
administrative edge is enabled on a port. BDPU filtering is configured
on a per-port basis. (Default: Disabled)
◆ Edge Port BPDU Guard – This feature protects edge ports from
receiving BPDUs. It prevents loops by shutting down an edge port when
a BPDU is received instead of putting it into the spanning tree
discarding state. In a valid configuration, configured edge ports should
not receive BPDUs. If an edge port receives a BPDU, an invalid
configuration exists, such as a connection to an unauthorized device.
The BPDU guard feature provides a secure response to invalid
configurations because an administrator must manually enable the
port. (Default: Disabled)
◆ Port Error Recovery – Controls whether a port in the error-disabled
state will be automatically enabled after a certain time. If recovery is
not enabled, ports have to be disabled and re-enabled for normal STA
operation. The condition is also cleared by a system reboot.
◆ Port Error Recovery Timeout – The time that has to pass before a
port in the error-disabled state can be enabled. (Range: 30-86400
seconds or 24 hours)