Conference 7.286::fddi

440.0. "FDDI/Ethernet" by GRANPA::DFAUST (Don't drink the Koolaid) Wed Jan 08 1992 15:41

    I have a customer that wants to install the following configuration
    
    
    
                           _________________
		___________|  FDDI Conc.   |______________
    		|	   |_______________|		  |
    		|		   |			  |
    		|		   |			  |
    	   _____|_____	      _____|_____	     _____|_____
    	  |  VAX     |	      |   VAX    |	     |   VAX    |
    	  ------------	      -----------	     ------------
    		|		   |			  |
    		|		   |			  |
       <--------|------------------|----------------------|---------> Other
     Other                     Ethernet                             Systems
       Systems
    
    1. How do you ensure that the traffic between the VAXes uses the FDDI,
    but that it automatically fails over to the Ethernet when a problem
    occurs?
    
    2. How would you know a problem occured, other than the obvious
    reduction in throughput?
    
    Any help would be appreciated.
    
    Dennis Faust
    

Whether/how that works depends on the protocol.  What protocols are you
dealing with?

	paul

For TCP/IP I don't know the answer.

For DECnet, you can get the result  you want by making each of the VAXen
routers.  The two LANs (FDDI and Ethernet) must NOT be bridged together.
(That restriction goes away in Phase 5 if you use Phase 5 style addressing.)
Set the circuit cost on the Ethernet higher than that on the FDDI.  That
will make the FDDI the preferred path to any neighbor that's reachable
that way.

	paul

    Thanks alot. I thought that might be the answer but I wasn't sure. I
    appreciate the input.
    
    Dennis
    

If those 3 VAX systems happen to be part of the same VAXcluster system, you can
use the LAVC failure analysis capability to notify you of failures (see the VMS
5.4-3 Release Notes for details).