Alcatel-Lucent 7750 SR OS Service Manual page 491

priority
Syntax priority bridge-priority
no priority
Context config>service>vpls>stp
Description
The bridge-priority command is used to populate the priority portion of the bridge ID field within
outbound BPDUs (the most significant 4 bits of the bridge ID). It is also used as part of the decision
process when determining the best BPDU between messages received and sent.
All values will be truncated to multiples of 4096, conforming with IEEE 802.1t and 802.1D-2004.
The no form of this command returns the bridge priority to the default value.
Default
By default, the bridge priority is configured to 4096 which is the highest priority.
Parameters
bridge-priority — The bridge priority for the STP instance.
priority
Syntax priority stp-priority
no priority
Context config>service>vpls>spoke-sdp
config>service>vpls>sap>stp
Description
This command configures the Alcatel-Lucent Spanning Tree Protocol (STP) priority for the SAP or
spoke SDP.
STP priority is a configurable parameter associated with a SAP or spoke SDP. When configuration
BPDUs are received, the priority is used in some circumstances as a tie breaking mechanism to
determine whether the SAP or spoke SDP will be designated or blocked.
In traditional STP implementations (802.1D-1998), this field is called the port priority and has a value
of 0 to 255. This field is coupled with the port number (0 to 255 also) to create a 16 bit value. In the
latest STP standard (802.1D-2004) only the upper 4 bits of the port priority field are used to encode
the SAP or Spoke SDP priority. The remaining 4 bits are used to extend the port ID field into a 12 bit
virtual port number field. The virtual port number uniquely references a SAP or spoke SDP within the
STP instance.
STP computes the actual priority by taking the input value and masking out the lower four bits.The
result is the value that is stored in the SDP priority parameter.
masking out the lower 4 bits results in a parameter value of 0. If a value of 255 is entered, the result is
240.
The no form of this command returns the STP priority to the default value.
Default
128
Parameters
stp-priority — The STP priority value for the SAP or Spoke SDP. Allowed values are integer in the
7750 SR OS Services Guide
Values
Allowed values are integers in the range of 4096 — 65535 with 4096 being the
highest priority. The actual bridge priority value stored/used is the number entered
with the lowest 12 bits masked off which means the actual range of values is 4096
to 61440 in increments of 4096.
range of 0 to 255, 0 being the highest priority. The actual value used for STP priority (and stored
Virtual Private LAN Services
For instance, if
a value of 0 is entered,
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