Conference 7.286::fddi

2246.0. "Redundant FDDI setup" by NETRIX::"[email protected]" (Jurgen Caeyman) Thu Apr 10 1997 12:42

Hi,

At Digital Brussels we have the following LAN setup :

- GigaSwitch/FDDI.
- DEChub 900 with DECswitch 900EF modules connected in tree to the GS, on each
floor of each building on our campus.
- Furthermore we have an FDDI backbone ring connecting all the buildings from
before the introduction of the GigaSwitch. On this ring a number of FDDI
concentrators as well as the Gigaswitch are connected..

In this setup the GigaSwitch is a single point of failure for the entire LAN.
I wanted to use the above "old" FDDI backbone ring as a failover in case the
GigaSwitch fails. 

1 : 
By connecting the M port of the 900EF to the concentrator and the S port of
the 900EF to the GigaSiwtch. Of course an M-M connection wan't work with the
concentrator. In this setup the 900EF port are configure M/S in front.
Can the concentrator be configured as to accept M-M connections as does the GS
?

2:
When configuring the 900EF as A/B port in front I got green lights yet I'm not
quite sure if this is a valid setup  nor how it works:
  900EF A -  M of concentrator
  900EF B - M (or is it S ?) of Gigaswitch
Remember the concentrator and the GigaSwitch already sit on the same FDDI ring
as well.

Could someone comment on this or give me any other suggestion how I can build
in some redundancy without having to buy a second GS/FDDI so I can save some
money for DEC.

Thanks In advance,

Jurgen Caeyman
Network Manager Digital Brussels
[Posted by WWW Notes gateway]

       There is a great deal of discussion in the NPSS::GIGASWITCH notes
    conference regarding redundant configurations.  Most of it can be found
    by looking under the keyword failover-configurations.
    
       The classic topology which most GIGAswitch/FDDI customers use is
    dual homing with two GIGAswitch/FDDI systems.  The active "B"
    connections go to one GIGAswitch/FDDI system, the standby "A"
    connections go to the other GIGAswitch/FDDI system.  The two
    GIGAswitch/FDDI systems are interconnected, usually with a hunt group.
    
        If you don't have the money for two GIGAswitch/FDDI systems, then
    you can dual home to a single ring using concentrators.  The active "B"
    connections go to the GIGAswitch/FDDI system, and the standby "A"
    connections would go to the concentrators.
    
        Of course you will have a substantial drop in throughput after a
    failure.
    
    MDL
    
    P.S. M-M is about the only completely illegal FDDI configuration.