You'll have to forgive me, I'm not entirely familiar with how networking on VMS works at this level. Can you setup something that uses pseudo devices but doesn't require promiscuous mode and see if that works? If so then I think we can definitely narrow it down to your promiscuous theory. If that's the case it just then becomes a question of is the issue with the pseudo devices themselves or the way PCAP is setting them up? I have no idea what I'm talking about, by the way. Just thinking out loud. :) -brian On Sep 19, 2012, at 19:25, Peter Coghlan <HECNET at beyondthepale.ie> wrote: I would also like to run multible instances of simh. This works fine for me as long as only one of them tries to do networking. Once I attempt to start networking on a second instance, the networking on the first instance stops working. This makes it difficult to run a vaxcluster on my alpha :-( How are the simh instances sharing the Ethernet interface? I don't really know. It appears a new EWA pseudodevice is created for each instance. However, PCAP-VMS seems to require the pseudodevice to be in promiscuous mode and I suspect that this is only allowed for one of them. It's not clear to me whether networking is even supposed to work for multiple instances. I should try installing an extra ethernet adapter and see if that allows it to work. Regards, Peter Coghlan.