[Info-vax] LAT query

[Hans Bachner]

Hans Bachner schrieb am 07.01.2021 um 20:14:
> Rich,
> 
> Rich Jordan schrieb am 05.01.2021 um 17:50:
>> Running into a novel (for me) LAT issue.  We have a site with a DS20 
>> and a DECserver 708 with current software.  LAT is used for a couple 
>> of faxmodem connections and one management terminal that still 
>> connects that way.
>>
>> We are putting an emulator in to replace the alpha.  The machine was 
>> setup offline, IP and DECNet address changed but we missed adding a 
>> service name parameter to the LAT startup so when it initially booted 
>> on the customer network, it also presented the same LAT service name 
>> as the actual Alpha.  That was quickly corrected, the emulator 
>> rebooted, and the emulator now has its separate LT service name.  The 
>> emulator and the alpha are on the same subnet/VLAN/switch with no 
>> filtering or load balancing or other possible known problem causers.
> 
> Did you configure the emulator to use the same MAC address as the 
> physical DS20? This must be avoided if they are in the same LAN 
> (specifically: same broadcast domain). Different DECnet addresses 
> should/might hide this problem, but it's better to avoid that in the 
> first place.
> 
>> Now the DECserver keeps 'losing' the alpha and the emulator as 
>> services it will connect to.  Only one of them shows up as an 
>> available service at a time, either 'alpha' or 'emu'.  You cannot 
>> connect to 'alpha' when the DECserver sees 'emu' and vice versa.  The 
>> services on both machines appear to be running normally.  One day (or 
>> for several hours) one will be available, then for reasons unknown it 
>> switches to the other.
>>
>> We can bounce the decserver if that is likely to help, but I don't 
>> recall ever seeing behavior like this before, albeit with older 
>> DECservers than the 708.  Any ideas?
>>
>> Thanks
> 
> Make sure LAT is started after DECnet during system startup. On the 
> running system, stop LAT ($ MC LATCP SET NODE /STATE=OFF if LAT is not 
> actively used by some process) and restart it with
> $ @SYS$STARTUP:LAT$STARTUP
> 
> If this does not help, please post the results of the following commands:
> 
> - on both physical and emulated Alpha:
> $ MC LATCP SHOW NODE
> $ MC LATCP SHOW SERVICE <service-offered-by-this-node>
> $ MC LATCP SHOW LINK /FULL
> 
> - on the DECserver:
> Local> show node <ds20>
> Local> show service <service-on-ds20>
> Local> show node <emulated>
> Local> show service <service-on-emulated>
> 
> Thanks  regards,
> Hans.

Btw, it should not be a problem for the DECserver to see the same 
service offered by multiple nodes. In fact, this is a feature of LAT 
which helps to achieve load balancing and failover.

Hans.