Alcatel-Lucent 7750 SR OS Service Manual page 406

Configuring a VPLS Service with CLI
bigger than the 12 bits definable in a configuration BPDU. STP takes the internal representation
value of a spoke SDP and identifies it with it's own virtual port number that is unique to every
other spoke SDP defined on the VPLS. The virtual port number is assigned at the time that the
spoke SDP is added to the VPLS.
Since the order in which spoke SDPs are added to the VPLS is not preserved between reboots of
the system, the virtual port number may change between restarts of the STP instance. To achieve
consistency after a reboot, the virtual port number can be specified explicitly.
CLI Syntax: config>service>vpls>spoke-sdp# stp
Spoke SDP Priority
Spoke SDP priority allows a configurable tie breaking parameter to be associated with a spoke
SDP. When configuration BPDUs are being received, the configured spoke SDP priority will be
used in some circumstances to determine whether a 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 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 spoke SDP within the
STP instance. See
number.
STP computes the actual spoke SDP priority by taking the configured priority value and masking
out the lower four bits. The result is the value that is stored in the spoke SDP priority parameter.
For instance, if a value of 0 was entered, masking out the lower 4 bits would result in a parameter
value of 0. If a value of 255 was entered, the result would be 240.
The default value for spoke SDP priority is 128. This parameter can be modified within a range of
0 to 255, 0 being the highest priority. Masking causes the values actually stored and displayed to
be 0 to 240, in increments of 16.
CLI Syntax: config>service>vpls>spoke-sdp>stp#
Page 406
port-num number
Range:
1 — 2047
Default:
(automatically generated)
Restore Default: no port-num
Spoke SDP Virtual Port Number on page 405
priority stp-priority
Range:
0 to 255 (240 largest value, in increments of 16)
Default:
128
Restore Default: no priority
for details on the virtual port
7750 SR OS Services Guide