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Conference netcad::hub_mgnt

Title:DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:NETCAD::COLELLADT
Created:Wed Nov 13 1991
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:4455
Total number of notes:16761

4376.0. "MS624T ... no loop warnings?" by SCASS1::auodial1_port7.auo.dec.com::korns () Thu Apr 24 1997 18:43

There appears to be a bug in either clearVISN V1.1a or the MultiSwitch
624T relating to loop detection. As a result, it is VERY easy to create
repeater/non-spanning-tree-switch loops that require jerking the power
to correct.

Even with 'Loop protection' enabled on MS624Ts, there are NO warnings
when dragging down group connections to backplane channels. The MS612EX
does provide loop warnings, but not the MS624T. 

It is a very common situation (out-of-the-box or after hot swap) to have 
an MS624T with it's default thinwire connection connected to the
back[stack]plane's thinwire and then drag a group-1 or group-2 connection
down to another flexlan channel that might be tied to a MS612EX switch
which also connections to the thinwire. Boom! no warning and you got a 
tight loop that lock on the transmit lights on all LANs. I've found no
way out of this without pulling power. 

MultiSwitch Hub 624T .. HW=v2, RO=v01.05, SW=V1.0.0
MultiSwitch 612EX ..... HW=D/D,RO=J,SW=V1.0

dave

T.RTitleUserPersonal
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4376.1Only Checks Repeater LoopsNETCAD::DRAGONFri Apr 25 1997 09:1911
    
    Dave,
    
    	MCM only checks for repeater loops. It does not include switches
        in its detection algorithm. In addition, the Switch 612EX does
        not support STP. Because of this combination it is easy to create
        a loop as you have found. This doesn't help your situation, but I
        thought that some explanation was needed.
    
    Bob
    
4376.2see note 4275 for ways to avoid loopsNETCAD::MOWERSun Apr 27 1997 23:112
  Also, see note 4275 on ways to avoid switch loops.
  Carl.
4376.3You get what you pay for...PTOSS1::DANZAKPittsburgher �Tue Apr 29 1997 23:1211
    You get what you pay for....cheap switch = no loop detection.
    
    Of course...some TRAINING and a 'how to' book with the product would
    help. (hint hint)  Bay publishes some WONDERFUL little reference books
    on survival with their products.  That's how you get customer loyalty -
    help them out etc. (hint hint)
    
    And, of course, everything costs money, time etc.  but customer focus
    always wins....
    j
    
4376.4Gee Jon....which is it you *really* want? :-)NETCAD::BATTERSBYWed Apr 30 1997 10:1818
    >Of course...some TRAINING and a 'how to' book with the product would
    >help. (hint hint)  Bay publishes some WONDERFUL little reference books
    >on survival with their products.  That's how you get customer loyalty -
    >help them out etc. (hint hint)
    
    Your statement appears to be an oxymoron, based on what you've told
    us in the past in here. :-)
    
    Jon, you keep telling us that your customers don't have time or
    don't want to bother reading all the nice documents and literature
    that are provided or are available now. :-)
    We provide release notes, quick-start guides, and the normal
    installation guides to help customers get their stuff installed, 
    powered up, and in use, and all we hear is that no one reads this
    stuff, and that customers don't want to flog through a lot of manuals
    or reference books.
    
    Bob
4376.5IROCZ::D_NELSONDave Nelson LKG1-3/A11 226-5358Wed Apr 30 1997 11:0623
RE: .4
               -< Gee Jon....which is it you *really* want? :-) >-

I suspect that Jon and his customers want what we'd all really like to have:

	a) a small, simple, comprehensive document that tells you in plain
	language all the things you have to do to make the product work, all 
	the limitations, all the special exceptions, all the common human 
	errors, and

	b) a product so well engineered and so plug-'n-play that all of the 
	above fits on one side of a 3" x 5" card, in 12-point type.

Oh, any by the way, it should be inexpensive and highly reliable, too.  :-)

I say this only partly tongue-in-cheek.  This is really what we should be
striving for in terms of engineering excellence.  All too often time-to-market
gets in the way, however.

Regards,

Dave

4376.6MCM Switch-Rptr Loop Detection, place your vote hereSCASS1::auodial1_port7.auo.dec.com::kornsThu May 01 1997 12:0925
I don't know how I missed note 4275. I thought I searched for the 
word 'loop' before putting my basenote in. Maybe not. Thats a very
good explaination.

I place a strong vote that MCM be modified to check for switch-repeater
loops as well. And if it's too costly to check if the switch(s)
have spanning tree or not, I vote to have an ARE YOU SURE? dialogue
box pop up even if/when a loop member really supports spanning tree.
It's much easier to justify to a paying customer that they hosed
themselves if they just got done clicking [YES] to a dialogue box
that that said ARE YOU SURE? 

FWIW, between my demo unit and a pair of customer units staged at a
reseller, we've created the condition nearly a dozen times. The
last few times it occured, was after we understood the problem but
where careless and re-created the condition accidently. The most
embarrasing was when the reseller was doing training for the customer.
After a MS624T hot swap (which re-connects the module to the thinwire)
and restoring it's flexlan connect, we forgot to unconnect the
TW connection first, Boom! 

Place your vote as a reply here!!!

And CSC support folks, I'd be curious to hear how many support calls
are coming in on this ...
4376.7TechTip Published?SCASS1::auodial1_port7.auo.dec.com::kornsThu May 01 1997 12:195
No more thing, Note 4275 looked like a formal TechTip to me so I
was surprised when I didn't find it on our web page. Is it out 
there somewhere and I just can't find it?

Dave
4376.8BOTH are needed for different design centersPTOJJD::DANZAKPittsburgher �Fri May 02 1997 16:3418
    re: Short and long...
    
    You need BOTH.....
    
    You need things that are simple, easy to use, quick to install and
    function as they should....
    
    HOWEVER>..as you scale up you need more in-depth detailed information
    for the 'problems from hell'.
    
    We MUST do both - ease for the low end and extensive for the high end.
    
    Nobody wants to read anything UNTIL they really HAVE to...but when they
    HAVE to, they need to have it now!
    
    (case in point, DECserver documentation - nice, but no easy to use and
    how to so most folks bought Shiva because they never realized the
    features the DECserver has....etc.)