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Conference netcad::hub_mgnt

Title:	DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:	Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:	NETCAD::COLELLADT

Created:	Wed Nov 13 1991
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	4455
Total number of notes:	16761

4412.0. "FFDI Ring in-hub connection limit ?" by CHEFS::HARVEY (Baldly going into the unknown...) Wed May 14 1997 14:54

       Simple enough query...
  
       I just configured a 900 hub with 2 x 900EF switches and 5 x PEswitches 
       plus a PORTswitch in the last slot. Using MCM I created an FDDI ring in 
       the hub and proceded to connect all the PE's and 900EF's to it. All 
       went fine until I came to the last PE switch where MCM stopped me from 
       making the connection. 
  
       Is there a fixed limit as to the max no. of connections to such an 
       internal FDDI ring ?  I checked it wasn't the individual module by 
       removing one connection and making with the last one which wouldn't 
       connect. I also duplicated across a second of the customer's hubs 
       configured the same way.
  
       No problem are involved I just need to know as part of the on-site 
       training I am about to deliver as to whether this is a hard limitation.
  
       Thanks
  
       Rog

T.R	Title	User	Personal Name	Date	Lines
4412.1	Does this help?	SNOFS1::KHOOJEANNIE	Laziness breeds Efficiency	`Wed May 14 1997 22:27`	20
	Hi Rog There are 14 flex channels available on the lower connector, and each FDDI connection uses 2 flex channels. For a dual ring internal to the hub for 7 modules, you need 7 connections (switch 1-switch 2, 2-3, 3-4 ... and 7-1) (14 flex channels), which should be OK if you don't use any of the lower connector's flex channels for Ethernet. i.e. if you have this dual ring, you can only use the thinwire and the upper connector's flex channel for Ethernet. If you connected these switches in an FDDI tree or a dual ring external to the hub, then you would only need 6 connections (12 flex channels). Regards Jeannie
4412.2	Is this the same for the F/w upgraded hubs too ?	CHEFS::HARVEY	Baldly going into the unknown...	`Thu May 15 1997 05:46`	6
	Thanks for the reply. All is clear(er) now. Does this hold true for the firmware upgraded hub which has more Flex channels available - 16 in the lower connection block ? Rog
4412.3	you can't teach an old dog new tricks...	JOBURG::RYAN	There'll be days like this	`Thu May 15 1997 10:38`	11
	Yes, since our existing FDDI modules, such as the DECswitch & PEswitch, don't know about the extra channels. If you can get a hold of the VNswitch 900/ATMswitch 900 presentation, there's a nice diagram of the backplane in there which should finally clear it up for you - I know it worked for me. Ryan NPBU, South Africa
4412.4	FDDI PHYSICAL nature	ULYSSE::virenq.vbe.dec.com::ULY2::HEMMINGS	Lanterne Rouge	`Wed May 21 1997 03:11`	16
	I think the important issue is that of the physical nature of FDDI. This has been hinted at in replies to the note, but not stated definitatively. I take the liberty of posting the relevant paragraph from the FDDI configuration guide, which is available in the public directory on NAC - "First, realize that ANY FDDI connection between two adjacent stations is actually two POINT to POINT connections no matter where the stations are in the configuration (tree or dual ring). This is a basic fact for any vendor's FDDI products, whether they are in a hub or not. The backplane of the DEC- hub 900 is used to make these point to point connections between DECconcen- trators, FDDI DECswitches or PEswitches in the hub. One backplane channel is needed for each connection. Since two connections are required between any two ports, TWO backplane channels are required for each connection between any two ports on DECconcentrators, FDDI DECswitches, or PEswitches, regard- less of the actual configuration."