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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

316.0. "Hubs connected together only with mgnt cable" by RULLE::KLASSON (Sven-Olof Klasson @GOO) Tue Jul 27 1993 12:28

A customer are going to configure a number of DEChub90 like this.

  +---------+  +---------+  +---------+  +---------+
  | DEChub90|  | DEChub90|  | DEChub90|  | DEChub90|
  |         |  |         |  |         |  |         |
  |         |  |         |  |         |  |         |
  |         |  |         |  |         |  |         |
  |         |  |         |  |         |  |         |
  +----+----+  +----+----+  +----+----+  +----+----+
       |            |            |            |
       |            +----------+ | +----------+
       + --------------------+ | | | One ethernet segment for each DEChub90
                             | | | |
                           +-+-+-+-+-+
                           |DECNIS600| 
                           |         |
                           |         |
                           |         |
                           |         |
                           +----+----+
                                |
                                |          Backbone ethernet
           ---------------------+----------------------------


A lot of repeaters will be installed in the DEChub90's and this will connect
to PC's. There are no DECbridge90 in the hubs.

The customer wants to manage the repeters with DECagent90 and HUBwatch. As
the repeters only can be managed via the management bus from a DECagent90
or a DECbridge90 there must be a DECagent90 in each hub.

One way could be to install DECbridge90 in three hubs, and a DECagent90 in
the forth hub. However this might not be a good idea since bridging is done
by the DECNIS.

An other way could be to connect the hubs as two pairs to reduce the number
of DECagent90 required. But the customer cant allow any downtime and wants
to keep the ethernet segments separate in the hubs to isolate faults.

The customer plans to keep the ethernet segments separate (each hub connected
to DECNIS) but connect two hubs together with the management cable.
This will reduce the number of DECagent90 needed to two. After reading 303.4
I understand this is possible.

Is this a good way to configure? 

An important issue is uptime in this configuration. Can a fault on the 
management cable disturb ethernet trafic in a hub?

What is the limit on the length of the management cable? 


Sven-Olof Klasson

T.R	Title	User	Personal Name	Date	Lines
316.1	Need DECbridge with DECagent V1.1	QUIVER::GAUDET		`Tue Jul 27 1993 16:55`	6
	You must have a DECbridge in each hub (or one per double hub if you daisy-chain) in order to manage the repeaters with V1.1 of the DECagent 90. V1.1 will not do direct backplane management. Roger Gaudet DECagent 90 devo
316.2	More questions	RULLE::KLASSON	Sven-Olof Klasson @GOO	`Wed Jul 28 1993 05:16`	21
	Roger, Thanks for pointing out that DECagent90 V1.1 don't do direct backplane management. Today I read 81.6 that tells that direct backplane management might be in V2.0 of DECagent90. Will direct backplane management be in DECagent V2.0? When is V2.0 planned to be released? Back to the configuration in .0. Given the fact that a DB90 is needed. Is it a good idea to connect to DEChub90 together with ONLY the management cable (with a DECbridge90 in each pair of hubs)? Any risk that a DEChub90 can be made inoperative by any fault on the management cable? Thanks Sven-Olof
316.3		NAC::FORREST		`Tue Aug 03 1993 15:48`	28
	> Will direct backplane management be in DECagent V2.0? That's our plan. >When is V2.0 planned to be released? The plan is for a December release, but it's too early to tell if we are certain to make it. >Is it a good idea to connect to DEChub90 together with ONLY the management >cable (with a DECbridge90 in each pair of hubs)? No, it's not a good idea. Each DECbridge 90 will hear Ethernet source addresses from only one hub to build its forwarding table. Therefore, it cannot map the addresses in the other hub to repeater ports. >Any risk that a DEChub90 can be made inoperative by any fault on the management >cable? Each module is perfectly happy if it never get polled. The bridge though, will spend a lot of time waiting for responses. The only risk I can think of is if the fault causes garbled bits on a command to a repeater - you could shut off the wrong port, including port 0, which connects the repeater to the backplane.