Conference netcad::hub_mgnt

    Your question does not compute. Could you explain in a little more
    detail what you are trying to do? I think the docs don't discuss it 
    because there is no difference between port 2 and port 7 (except maybe
    that one MAC address is lower than the other).
    
    -Mike

    Sorry for being unclear.  I'm trying to understand the DECbridge 900MX,
    it's seven ports, and how they work in a DEChub 900.  I understand how
    ports can be connected to the front (the FDDI, AUI and TP connectors on
    the front of the bridge) or to the back (the hub backplane with is
    several configurable segments).  What I don't understand is what
    experimentation seems to indicate are some unwritten rules:
    
    1.  In our testing, it seemed that port 1 (the FDDI port) and port 2
    (one of the AUI ports) passed different data, in that it seemed port 2
    would not connect via a fiber transceiver to our main network, while
    port 1 would.  I heard that the DECbridge 900MX would only connect
    'out' on port 1.
    
    2. It seems that data that comes into any bridge port is sent to all
    other bridge ports, whether they are connected to the same DEChub 900
    backplane segments or not.  Does the bridge have a non-disableable
    cross-bar within itself, connecting all ports?
    
    I know these questions sound stupid, but I can't reconcile the results
    we see when using the bridge with the scanty information available in
    the DECswitch 900EF guide.
    
    Thanks for your patience.
    tl

    I'll see if I can address the questions in the previous reply.
    
    Q1:
    To help answer question 1 I'm going to have to ask a question.
    When you say you have port 2 (the first of 2 AUI ports), connected
    to your main network via a fiber transceiver, what kind of fiber
    transceiver is being used? Also it sounds like you have an alternative
    path to your main network via FDDI. If you are using the DEFLM
    fiber transceiver, remember, this is a 10baseFL MAU, not an FDDI MAU.
    
    Q2:
    The bridge is a store & forward bridge which will internally and 
    externally forward all traffic to and from all ports. Each Ethernet 
    port has its own CLANCE chip, descriptor memory, and a chunk of
    packet memory allocated to it. Likewise the FDDI port has its own
    set of buffers allocated to it for traffic. So the processor engine
    simply executes an arbitration algorythm for handling the packet
    traffic flow between ports. By default all traffic is internally 
    forwarded to all ports by virtue of natural filtering (learning).
    That is, all ports learn the MAC address of all other active ports.
    
    Hope this helps answer your questions.
    
    Bob

    I should correct myself a little. I think I may have suggested
    that all ports forward all traffic all the time. I really didn't
    mean that. The bridge ports go through a learning period where
    each port "learns" what MAC addresses it can hear. Then when packets
    start arriving, the packets are only forwarded to the ports where
    the destination address was learned to have been seen last. Now
    multicast packets *will* be forwarded to all ports.
    Sorry for the small confusion, I hadn't had my first cup of high-test
    (coffee), yet to start my own "engine".
    
    Bob

    >1.  In our testing, it seemed that port 1 (the FDDI port) and port 2
    >(one of the AUI ports) passed different data, in that it seemed port 2
    >would not connect via a fiber transceiver to our main network, while
    >port 1 would. 
    
    Not sure what you mean by "port 2 would not connect", thus Bob's
    questions about the transceivers etc. If you mean that the port status
    LED blinks, it means the port is blocking. 
    
    If you connect the FDDI port (port #1) to your network, and also
    connect port #2 to the same network segment, the spanning tree
    algorithm will force port #2 into blocked state. This is to prevent
    duplicate packets and loops.
    
    > I heard that the DECbridge 900MX would only connect
    >'out' on port 1.
    
    You heard wrong. But I guess it depends on how you define "connect
    out".
    
    -Mike
    
    p.s.  For the most part they are not "unwritten rules". Have a look at
    the book in note #2771, it will explain bridging better than we can,
    and it has better jokes than you'll get here, to boot.
    

    Hi
    
    I'd like to re-open (with more information) this discussion.  Here's a
    thumbnail of a theoretical LAN topology:
    
    			Remote Access LAN (modems/DECservers)
    		+-------------------------------------------+
    			    |				|
    			DECrepeater		    DECbridge
    			   90FL			      900MX
    			    |	Routable		| Non-routable
    			    |	protocols		| protocols
    	 _______	    |	(IP)	 _______	| (LAT, NetBEUI)
    	/	\	+-------+	/	\	|
    	| FDDI 	|-------+ DECNIS+-------| FDDI  |	|
    	\_______/	+-------+	\_______/	|
    	    |				    |		|
    	   |B|--------------+--------------|B|		|
    			    |---------------------------+
    
    I'd like to get rid of the DECrepeater, and use two ports on the
    DECbridge 900MX.  I want to set one port to filter all routable
    protocols, set another port to filter all non-routable protocols, and a
    third port to connect to the DEChub 900 backplane.
    
    Would this be an illegal configuration?  Is the DECbridge 900MX the
    right box for the job?  Do I need to use the brouter software to do
    what I need?
    
    Thanks!
    tl
    

    Hi
    
    How can I clarify the problem in -.1?  I'd like to understand, resolve
    and move on.
    
    Thanks!
    tl