https://bugtraq.ru/library/books/stp/script/

#!/bin/sh
#
# Copyright 2001 Vladislav V. Myasnyankin, Yekaterinburg Russia
# hugevlad@yahoo.com http://cybervlad.port5.com
# All rights reserved.
# 
# WARNING! Be very careful, because you can occasionaly crash
# your network.
#
# SEE DISCLAMER IN MAIN PROGRAM 
#
# note:
# all numbers can be like 00010203040506 or like 00:01:02:03:04:05:06
#

device=eth0             # ethernet device name (default - eth0)
dmac=01:80:C2:00:00:00  # destination MAC (default - 01:80:C2:00:00:00)
smac=00:01:38:00:b4:c7  # source MAC (default - MAC on given
                        # or default device)
proto_id=0000           # Protocol Identifier (hex, 2 bytes)
proto_v_id=00           # Protocol Version Identifier (hex, 1 byte)
bpdutype=00             # BPDU type (hex, 1 byte)
flags=00                # flags value (hex, 1 byte)
rootid=800000013800b4c7 # Root Identifier (hex, 8 bytes)
rootpc=00000000         # Root Path Cost (hex, 4 bytes)
brid=800000013800b4c7   # Bridge Identifier (hex, 8 bytes)
portid=8002             # Port Identifier (hex, 2 bytes)
mage=0000               # Message Age (hex, 2 bytes)
maxage=1400             # Max Age (hex, 2 bytes)
hellotime=0200          # Hello Time (hex, 2 bytes)
fdelay=0f00             # Forward Delay (hex, 2 bytes)

./stp -v -dev $device -dmac $dmac -smac $smac -protoid $proto_id\ 
-protovid $proto_v_id -bpdu $bpdutype -flags $flags\
-rootid $rootid -rootpc $rootpc -brid $brid -portid $portid\
-mage $mage -maxage $maxage -htime $hellotime -fdelay $fdelay