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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

1904.0. "DECconcentrator 900MX & Bridge900 EF problem" by STROP::LAYLAND (Iligitami nil Carborundum) Wed Jan 18 1995 11:38

Hi  I have a customer who claims he has found a problem with a conc 900MX and
bridge 900EF configuration.

                                Hub900
                                900MX
                        +=====+======+======+
FDDI                    |     |      |      |
                        |     |      |      |
                    900EF   900EF  900EF   900EF
Ethernets            |        |      |       |
                     1        2      3       4

The bridges are in  Hubone units the concentrator is in the 900hub. The customer
inadvertantly connected two ethernets together ie 1 & 2. He  didnt' notice.
Spanning tree should have put one link into backup.When he returned the next day
nothing was working. After resetting the whole system only three 90EFs were
working. Moving the failing EF to a new PMD got it working again.
I am not sure if I have the whole story from the customer. He mentioned disabling
spanning tree on the EF, and reseting it all after it failed. My understanding 
is that spanning tree shouldnt' affect the Concentrator.


Regards John Layland UK NPBU.
T.RTitleUserPersonal
Name
DateLines
1904.1Wonder why customer felt he had to disable spanning tree?NETCAD::BATTERSBYWed Jan 18 1995 12:2221
    I would find out the following if I were you....
    
    1. Which of the 4 units the customer referred to as the "failing
       unit" (IE: which one wasn't "working" after the customer reset
       the whole system. Were there any error log entries noted when
       viewing the "broken unit" console after it was working again?
    
    2. Find out from the customer when exactly he disabled spanning
       tree, before connecting Ethernets 1 & 2 or afterwards. Also
       find out which of the EF's he disabled spanning tree on.
    
    If he disabled spanning tree *before* inadvertantly connecting
    Ethernets 1 & 2 together, this might explain why one of the links
    didn't go into backup. You can't detect loops if spanning tree is
    disabled.
    
    Sounds like he disabled spanning tree on a bridge, then inadvertantly 
    connected two LANs together. Why the rest didn't continue to work
    has me a little baffled.
    
    Bob
1904.2NETCAD::SLAWRENCEWed Jan 18 1995 13:314
    
    If he disabled spanning tree and then made a loop it would be amazing
    if it _did_ continue to work.
    
1904.3ANother way to Kill a Hub...MSDOA::REEDJohn Reed @CBO, (803) 781-9571 NIS NetworkerThu Jan 19 1995 09:3916
    I also have had HUBs stop working when I inadvertently plug the
    DECconcentrator FDDI UTP PMD modules into DECrepeater 10BaseT ports....
    
    That causes the Entire Ethernet portion of the hub to stop working, and
    all users to time out on all ports of all repeaters on a DEChub90,
    until you unplug the offending FDDI UTP source.  We found that the
    DECrepeater90 didn't segment this faulty port, but sent the signal into
    the HUB90 to propogate to the other modules.
    
    That might have been what he plugged into a DECbridge on his site?
    
    Keep the Spanning Tree running, and color code your jumper cables. 
    That is the only way that I can keep them straight.
    
    JR