Conference npss::gigaswitch

	Hi,

	Can someone give an advise on this configuration.

	Two GIGAswitches interconnected with DAS
	Each GIGASW/is using SAS cards
	DECSwitch900 EF DAS are dual homed on SAS card of different GIGASW.

	I can't verify that activity of the modules for the moment but I try to 
		realise what is happening.
	1. A and B port are CMT Thrue because connecetd on SAS
 	2. Only one MAC is present for the DECSWitch so the GIGASWitch(es) see
 	a loop and use the Spanning Tree to resolve the issue.
	
	
	My question is what, the point to use S interfaces rather than M ones.
	I the example above everything works due to spanning tree and if 	
	recovery need to be started (link failure) it will take more or less 	
	more 1 minute to recover from that event.
	Should it not be better to reconfigure the SAS ports of the GIGASW in 
	M port and use FDDI dual homing functionnality that will be faster to 	
	recover from link failure ?

	Thanks,
	Robert
	
	


	

        If the EFs are connected to "S" ports, then dual homing is not
    involved.  Dual homing in FDDI only refers to connections to "M" ports.
    
        Connecting a DAS device to two SAS devices results in a wrapped
    ring from a FDDI perspective.  From the perspective of spanning tree,
    all three devices are on a ring - spanning tree doesn't care about
    whether the ring is wrapped or not.
    
        Whether or not dual homing is preferable depends on the situation.
    In general, if you are trying to create a redundant configuration, dual
    homing yields faster failover times.
    
        There are lots of notes in this conference discussing redundant
    configurations - see the keyword failover-configurations
    
    MDL

    P.S. Spanning tree recovery using typical defaults will take less than
    a minute.  
    
    failover time = Max Age + (2 * Forward Delay)

	Taking the default values
	Max Aging Time =15 sec
	Forwarding Delay Time 15 sec
	we have 45 secs

	Robert