Conference 7.286::fddi

231.0. "DECbridge 500 Auto-Select Bug?" by LTLKNG::TAZBOY::ZIGLER (Tom Zigler DTN:432-7541) Tue Apr 02 1991 11:36

A customer has an 802.3/FDDI network comprised of the following components:

	- LAN Bridge 150s, all manually configured to run the 802.1 
	  Spanning Mode

	- DECbridge 500s (ROM V1.6 firmware)

	- DECconcentrator 500s

Initially, the "LAN Bridge 100 Spanning Tree Compatibility" parameter
for the first group of DECbridge 500s was manually set to a value of
"IEEE" via DECelms.  Subsequent examination of the "Spanning Tree Mode
Changes" parameter on these DECbridge500s revealed that this counter had
a value of zero (as one would expect).  At a later date, a second group
of DECbridge 500s was added to the network.  However, with this second
group, the "LAN Bridge 100 Spanning Tree Compatibility" parameter was
allowed to default to "Auto-Select", the normal default.  This time,
subsequent examination of the "Spanning Tree Mode Changes" counter for
THIS SECOND GROUP OF DECBRIDGE 500s ONLY, revealed an INCREMENTING
"Spanning Tree Mode Changes" counter.  Although the customer workaround
was to MANUALLY reset the "LAN Bridge 100 Spanning Tree Compatibility"
parameter to "IEEE" for all DECbridge 500s in this second group, I do
not understand why this manual setting is required.  It appears that the
"Auto-Select" feature fails in this scenario...is this a bug? 

Please advise.

		\Thanks in Advance

    
    	Could you tell me a little more about the network.  For example, are
    there any LAN Bridge 100s connected.  100s send out Digital Spanning
    Tree messages and would cause the spanning tree mode to change(initial
    setting is for IEEE 802.1d), thereby incrementing the counter.
    
    	Thanks,
    	Craig Michelson