From: pliuskon@intellistor.com (Saul Pliuskonis)
Subject: Weird 10Base-T Hub phenomena on Plexcom hardware - HELP!!!
Keywords: Plexcom, 10Base-T, Ethernet
Organization: Intellistor, Inc.
Date: Wed, 7 Oct 92 23:20:40 GMT


 We are running our Ethernet on 10Base-T and fiber, with hardware from Plexcomm.
 The fiber card is a model 8011, and the repeaters (c1, c2, etc...) are model 8023
 cards. The fiber tranceivers are model 8080.  The systems connected to these repeaters 
 are mostly Suns and PCs, all running TCP/IP. No other protocols are running on the 
 backbone.  The backbone that these cards are associated with is called "Ether C"; we 
 also have two other backbones called "Ether A", and "Ether B". Cards c2 through cx 
 are "Cascaded" off card c1. Card c1 is connected to a fiber card in the main wiring 
 closet via fiber traceivers connected to an AUI port on the c1 cards. The AUI port is 
 equivalent to port 12. 

    
               WIRING                                  WIRING
              CLOSET 3                                CLOSET 4
    
         
        c1     c2    c3     c4                       c1    c2    c3
        --     --    --     --                       --    --    --
       |1 |   |1 |  |1 |   |1 |                     |1 |  |1 |  |1 |
       |  |   |  |  |  |   |  |                     |  |  |  |  |  |
       |2 |   |2 |  |2 |   |2 |                     |2 |  |2 |  |2 |
       |  |   |  |  |  |   |  |                     |  |  |  |  |  |
       |3 |   |3 |  |3 |   |3 |                     |3 |  |3 |  |3 |
       |  |   |  |  |  |   |  |      Fiber Card     |  |  |  |  |  |
       |4 |   |4 |  |4 |   |4 |        MAIN         |4 |  |4 |  |4 |
       |  |   |  |  |  |   |  |       CLOSET        |  |  |  |  |  |
       |5 |   |5 |  |5 |   |5 |                     |5 |  |5 |  |5 |
       |  |   |  |  |  |   |  |         --          |  |  |  |  |  |
       |6 |   |6 |  |6 |   |6 |        |  |         |6 |  |6 |  |6 |
       |  |   |  |  |  |   |  |        |1 |         |  |  |  |  |  |
       |7 |   |7 |  |7 |   |7 |        |  |         |7 |  |7 |  |7 |
       |  |   |  |  |  |   |  |        |2 |         |  |  |  |  |  |
       |8 |   |8 |  |8 |   |8 |        |  |         |8 |  |8 |  |8 |
       |  |   |  |  |  |   |  |  ----->|3 |         |  |  |  |  |  |
       |9 |_____________   |9 |  |     |  |         |9 |  |9 |  |9 |
       |  |   |  |  |  |\  |  |  |     |4 |<--|     |  |  |  |  |  |
       |10|________ |10| \ |10|  |     |  |   |     |10|_______ |10|
       |  |   |  | \|  |  \|  |  |      --    |     |  |  |  | \|  |
       |11|___|11|  \11|   \11|  |            |     |11|__|11|  \11|
       |  |   \  |  |\ |   |\ |  |            |     |  |  \  |  |\ |
    ---|12|   |12|  |12|   |12|  |            |     |12|  |12|  |12|
    |   --     --    --     --   |            |      --    --    --
    |                            |            |      | 
    |                            |            | ------------ 
    |     ------------           |            | |  Fiber   | 
    |     |  Fiber   |           |            --|Tranceiver| 
    |-----|Tranceiver|-----------|              |          |
          |          |                          ------------ 
          ------------                          
  
  
      
 We are currently having the following problems:

 1) Systems connected to cards c2 and c3 in CLOSET 4 are unable to communicate with systems
  connected to cards c2 and c4 in CLOSET 3. Those same systems in CLOSET 4 are able to
  communicate just fine with systems on c1 and c3, in CLOSET 3, as well as with systems
  on the other two backbones. Systems on c2, and c3 in CLOSET 4 can also communicate
  between themselves, and with systems on c1.
  Systems on c1 in CLOSET 4 can communicate with everyone in CLOSET 3, as well as with the
  rest of the network, including backbones A and B. 

  I have contacted PLEXCOM's technical support, but they had no idea as to what could be
  causing it. I have tried plugging in spare repeaters, switching the order of the cascades
  off of the first card (c1), reseating all the cards, but to no avail.  I have tried 
  using network diagnostic tools to see if there are an abnormal amount of network errors,
  or collisions, but everything "looks" normal. 

 2) When I have my new Sun Sparc10 model 30 connected to card c2 in CLOSET 4 its network
  performance goes down the tubes. "ping -s somehost" can result in anywhere from 
  40-100% packet loss.  But when I connect the Sparc10 to card c1 in CLOSET 4 it works
  like a champ. Now the weird part. When I connect my Sun IPC to the exact same port on
  card c2 that the Sparc10 failed on, it works fine, 0% packet loss.  This behaviour
  is very repeatable. I have a call in to Sun about the Sparc10 problem, but I can't
  help feeling that it may be related in some way to problem #1.


If anyone has any clues whatsoever, I'd be very interested in hearing them.

Thanks,

SVP
-- 
 _______________________________________________________________________

  Saul Pliuskonis          e-mail address: pliuskon@intellistor.com   
  Intellistor, Inc.        USmail address: 2402 Clover Basin Dr.      
  (303)682-6515                            Longmont, CO 80503         
  fax (303)682-6401	   										   
 						   										   
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