[Info-vax] Loosing all LAT connections on one machine in DECNet Network

[H Vlems]

On 15 apr, 19:49, Chris Scheers <ch... at applied-synergy.com> wrote:
> JCamCMKRNL wrote:
> > I have a Dedicated network (10-Base5 ethernet) which only runs DECNet
> > traffic on it. This network has 5 Machines on it (four PDP-11/RSX11M+
> > and one VAX/VMS) and several DECServer 200MC terminal servers.
>
> > Recently on a few occasions (three times in the last three weeks) all
> > the LAT connections to the one VMS Machine are dropped. The users who
> > were logged in are disconnected, and their interactive process
> > terminates, returning them to the DECServer "Local>" prompt. When they
> > enter in the DECServer command "SHOW SERVICE" we see all the other
> > machines, but not the VMS Machine.
>
> > The VMS machine is still running fine, and there are no additional
> > device errors. We can still log into any one of the PDP-11 systems
> > through LAT on the DEC Servers, and then connect to the VMS system via
> > the SET HOST command, but still cannot connect to the VMS system via
> > LAT.
>
> > There were no Network messages logged to OPCOM, and the LATACP process
> > is still running. Later, time passes (sometimes several minutes, and
> > other times several hours) and the service returns with no apparent
> > reason or operator interaction. On one of these occasions we performed
> > a system reboot of the VMS system, but this did not restore the LAT
> > service for the system immediately. Instead, the LAT service came back
> > about 15 minutes after the reboot.
>
> > I tried using the LATCP program to see if I could do anything when it
> > was in this state, and it seemed to be working fine, but I still could
> > not connect from any terminal server.
>
> > Our basic topology is: All the 5 systems and one DECServer are in data
> > center connected to a DELNI hub, which in-turn is connected to the
> > thickwire 10-Base5 backbone. This Backbone runs throughout the plant
> > to several IDF communications closets. Some of these closets have one
> > DECServer connected to the Backbone directly via a transceiver and AUI
> > cable, and others have Multiple DECServers connected to a DELNI which
> > in-turn is connected via an AUI Cable to the Backbone transceiver.
>
> > When we loose all the connections to the one VAX system the LAT
> > service disappears on all DECServers throughout the plant, including
> > the one in the data center which is connected to the one DELNI with
> > the 4 PDP-11s and one VAX system.
>
> > I have DECNet network logging turned "ON" on the VAX, and see no
> > network OPCOM messages. I see no feature in LATCP to enable logging.
>
> > Based on this information I am reasonably sure that I am not dealing
> > with a hardware issue, because I can still connect to the PDP-11
> > systems via LAT and then connect to the VAX via SET HOST.
>
> > Is there a log file for the LATACP process?
> > Does anybody have any ideas as to how I might Diagnose this issue?
>
> > Any ideas would be deeply appreciated.
> > Jeff Cameron
>
> If it turns out that it is not hardware, is it possible that there is a
> PC (or other 100MB equipment) connected to the backbone somewhere?
>
> I had a similar problem with a DELNI/VAX/DECserver 200 environment once.
>   Periodically, LAT would go down, but DECnet would stay up.  (It did
> get noticably slower, though.)
>
> The DELNI was connected to the company network, which was primarily
> 100MB.  Periodically, something on the 100MB network would start
> generating enough data to swamp the 10MB DELNI, causing LAT to go down.
>
> When the storm passed, LAT came back.
>
> Putting a 10MB switch between the rest of the network and the DELNI
> solved the problem.
>
> --
> -----------------------------------------------------------------------
> Chris Scheers, Applied Synergy, Inc.
>
> Voice: 817-237-3360            Internet: ch... at applied-synergy.com
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>
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Excellent suggestion