I have a similar situation - 2 subnets. Different in that one is virtual so I can connect primary to my secondaries when I am 700 miles away.

My computers are using 4.05 - not a beta. Hopefully this is the same in 4.06b ( I need it for when I switch subnets when traveling.) To show you how to get the one you want, I deleted one of my secondaries on my primary computer, then reconnected using the desired subnet.

I choose "Configure Multiplicity" from the taskbar icon options, then KVM. For this demo, I deleted the secondary - do that if your desired secondary is configured (be sure you have the password to attach it again). Now, click the button on the right that has an encircled +. Do not enter the computer name - let Multiplicity scan the networks. Below is a picture showing the result of the scan for the secondary I deleted for this. The 117 result was clicked, then the "Add" button. The popup closed and the "Settings for NEARLYHEDLESNIK" came up. There the option to "Always use the IP address(blahblah)" was chosen as well as password entry and then "Save".

Hope this works for you.

Things seem to be working reasonably well for me now.  Here's what I have:

(1)  I'm using the 4.07 release instead of the 4.06 beta.

(2)  I am using IP addresses on my private Ethernet subnet instead of hostnames or the subnet that goes to the wireless router.

(3)  I have 4 machines: 3 Windows 11 and 1 Windows 10.  The primary is Windows 11.

(4)  I don't use Windows Firewall, but rather Norton 360.  My firewall rules look like this:

Under Program Control I have defined a rule for each of these programs: MultiplicityConfig.exe, MPRDP64.exe, MulltiPLV64.exe, MultiSrv64.exe, Multipl2_64.exe, MP2control_64.exe.

Each of the program rules divides allowed traffic into 2 types: Multiplicity traffic on IP addresses 192.168.2.11-192.168.2.14 (where my machines are) and ports 30564-30569 on a private network. The other type of allowed traffic (called Internet) is any protocol, any port, and any IP address on a public network.

I also defined a Traffic rule that says that all traffic on ports 30564-30569 must be in the IP address range 192.168.2.11-192.168.2.14 (where my machines are).

This seems to work, but I am uncertain that it keeps all Multiplicity traffic on the private subnet as I am unsure that I understand how the firewall works well enough.

I knew that I would remember something else to ask for.  I've had difficulty with taskbars.  I'm using Multiplicity to maintain several computers without having to get up and go to them.   I don't walk very well at all anymore, due to my health, and I use a Rollator (walker with 4 wheels).  Anyway. I need both the primary's and secondary's taskbars in KVM mode.  I found that the primary's taskbar overlays the secondary's if both are at the bottom, which makes sense.  I can put the secondary's taskbar at the top (with Start11), which does work, but is awkward for the person who usually uses that machine.  So, what I need is a simple, quick and unobtrusive way to move the taskbar while I am accessing that machine with Multiplicity.  Is there a command line option for Start11 (or anything else) that will move the taskbar the way I want?

I did not see your followup post after my suggestion; I came to report a problem with 4.07. I would have had to say "don't know what to do for this". Glad you are going.

Unfortunately MicroSoft must think users are stupid to want to move the taskbar from the bottom so they removed the capability to shift it in Windows 11. I will give you two options; it might be neither will work for you. Also a suggestion for Stardock that would help.

You are not alone in the taskbar problem - I had to deal with it, and believe there are a lot of others. My chosen solution is to use the "Display Setting" in Multiplicity. I have a 27" monitor and find that for my needs setting the KVM display to 75% size gets me by but can be a squint at times reading text. To set that, open Configure Multiplicity, then KVM and then click the advanced settings gear. Attached is a screenshot showing the configure menu and the opened advanced settings.

That is where Stardock could really help users. The choice jumps from 75% to 100%. My guess is that 95% would really do the job well to cover the MicroSoft taskbar boondoggle; should also provide 90% just in case.

The other option is one you will really have to decide for yourself.  The open source community has a program called "ExplorerPatcher" found on github. You might not be comfortable using open source software. If you are ok with such programs, read *everything* on github pages about ExplorerPatcher: there are important warnings and potential headaches due to WIndows 11 updates. I do not use it as I find the 75% solution works for me.

Yes, you are right.  Selecting a subnet would be fine for my purposes.

Thanks for the shrunk screen suggestion, I'll try it out.  Actually, one of my machines has a small screen, so I don't need to mess around withe taskbars with that machine.  I do wonder how the bigger screens will look when shrunk, though.  I'll find out.

P.S. - I'm a retired software developer too.