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From: pung@ornl-ncc.ARPA.UUCP
Newsgroups: mod.computers.vax
Subject: DEQNA and heartbeats
Message-ID: <8701310257.AA18159@ucbvax.Berkeley.EDU>
Date: Fri, 30-Jan-87 14:30:00 EST
Article-I.D.: ucbvax.8701310257.AA18159
Posted: Fri Jan 30 14:30:00 1987
Date-Received: Sat, 31-Jan-87 09:14:33 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: "M. S. Pung" <pung@ornl-ncc.ARPA>
Organization: The ARPA Internet
Lines: 55
Approved: info-vax@sri-kl.arpa



	We have a Delni which is configured as follows:
		1.  Several directly connected VAXes

		2.  An Interlink DEC/IBM gateway (Qbus Micro PDP-11)

		3.  An Applitek Bridge which supports an extended LAN 
		    across a three plant network.  Note that the 
		    Applitek Bridge is connected into one of the normal 
		    ports on the Delni not the "control" port.


	Everything was working fine until we connected another segment
	of Ethernet into the "control" port of the Delni.

	With the Delni switch in the "Global" position, the Micro PDP-11 
	console now continually displays NCP error messages along the 
	vein of "Collision Detect Test Failed" and "Short circuit".
	However when the Delni switch is in the "Local" position, the 
	Micro PDP-11 is extremely happy and quiet.

	After much discussion and testing, we have theorized the following:
		The Deqna on the Micro PDP-11 is sending out a heartbeat
		pulse and depending on the position of the switch on
		the Delni the heartbeat is either responded to (turned around)
		by the Delni ("Local" setting) or the heartbeat is not 
		answered by the Delni and/or the rest of the network ("Global").

	Apparently there is no way to disable the heartbeat function on
	the Deqna and since it is connected to the network via a Delni
	instead of an H4000, no one ever responds to the heartbeat and
	error messages result.


	My questions are the following:
	
	1.  Are our theories right or are we off base?

	2.  Is there a way to turn off the heartbeat function of a Deqna ?

	3.  Has anyone else seen this problem, (i.e. Deqna to Delni in "global")

	4.  Would changing some pins in the transceiver cable possibly disable
	    the sending of the heartbeat signal into the Delni ?



	Any help, comments, suggestions would be greatly appreciated.


					      Mike Pung
					Oak Ridge National Lab
				      Pung%ornl-ncc@ornl-msr.arpa
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