It turned out that the Windows XP problem was two things: I can't ping past the gateway of 10.0.2.2 in any OS (pinging is my go-to test for connectivity), and the IE in XP is too old for modern HTTPS connections. It took some futzing to find a site that had no HTTPS, but that connection is working.

I have better success with Google Chrome.

I do Firefox, but I can't change the browser because all of the modern sites are HTTPS and IE won't connect to download anything.

If I can figure out bridged networking I can import an FF install file that way. Not really important, I was just seeing how an ancient system would work. This is proving to be an education in different ways than I had figured on.

I solved the ReactOS video mode problem by telling virt-manager that I was installing Windows NT 4.0.

Frankly, I have no idea of how I solved the ISO changing issue, if it was anything I did, but it is working now.

The last couple of days have gotten me fairly far. My remaining outstanding problem is bridged networking. That is how I get data in to and out of the VMs that does not originate on the Internet.

To save people digging through the thread: I create a share on the host computer, and share it via NFS for Linux systems, and Samba for Windows systems. This lets me freely move data between the host and the VMs, and from VM to VM using the host as the relay point.

I'll resume chasing the bridged networking after the holiday weekend. For those in the US, Happy Thanksgiving! In the spirit of Alice in Wonderland, for the rest of the world, Happy Un-Thanksgiving!

Success!

The bridged networking situation has been resolved. Not as neatly as I'd like, but it has been resolved.

Somehow the setuid bit had been turned off on qemu-bridge-helper. I had turned it on previously, but things were still confusing at the time.

After I reset the bit, I am able to get out to my local network. I would prefer that it actually be on my network instead of a pocket network of 192.168.122.0/24, but I'll take it as I can reach into the pocket from my host. I haven't had a need to reach VMs from other devices, so not having a real presence on my LAN may not be a problem.

Some testing has revealed that, like most DHCP systems I'm familiar with, the bridge hands out the same address to the VM each time. This will let me use NFS to share between the host and the Linux VMs as the addresses will be persistent. Samba not being address-dependent will be OK now that I can reach my host.

Thanks to everyone for the help in getting here. {Insert the "happy Happy, Joy Joy" song here.}

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I was so tangled in getting networking to work at all, that I forgot something important until I tried replicating bits of my set-up. One thing I do is determine which systems go through a VPN based on an address range assigned by my router. In order to do this the NICs have to be visible to the LAN. These are set up infrequently, so I forgot about the issue.

Now I have more research to do. allend previously mentioned TAP, so I'm looking at that.

Success....again!

It took some finding, but I dug up a solution to bridging to the LAN.

First I had to remove the file /etc/libvirt/qemu/networks/autostart/default.xml to remove the virbr0 interface.

I added this to my /etc/rc.d/rc.local file:
I will admit to not fully understanding all of this, but I'll see what I can learn about it all now that I have it working. The part I find confusing is assigning a null address to eth0 and everything still works, the rest seems sensible. It seems that the address of 0.0.0.0 does not actually get set. Interesting.

The result is:

After changing my current VM Bridge settings to a device name of br0, booting the VM causes a tap# interface to appear on the host, with the # starting at 0 and incrementing for each active VM. The various VMs are being assigned addresses from my router as I want them to. I haven't tested reserving addresses yet, but I expect that to work correctly as I can see the VNICs in the router matching the address given out. VMs can connect to the host and each other, the host can connect to the VMs.

Somehow the eth0 and br0 interfaces share the same IP address, but it is working, so no complaints.

I'll let this setup run for a few weeks and see how it behaves.

The next adventure: Migrating my old Windows VMs to QEMU without invalidating the registrations. This one may actually be impossible. :-)

Quick follow-up. The reservation of addresses works as it should.

A pound to a penny on it not working. Different hypervisors are seen as different hardware as far as a Windows install is concerned.

That would appear to be the case. Both Windows 7 and Windows 10 went unregistered. My attempt to copy over Windows XP failed. It crashes while booting with a quick blue screen then a 30 second countdown to a reboot which blue screens...

Windows have some different requirements on QEMU/kvm than Linux distributions. Mostly in regards to the "normal" drivers not working in the Windows guest, so you need to take extra care to chose compatible options FOR the guest in the host VM setup, and possibly do some juggling in Windows after. That's maybe a good day of research and experiments.

On my system I can select the location of the install ISO by using the browse button then the browse local button. The first one that opens is the last used directory but the browse local allows navigation in the file system..

More updates as I continue tinkering with my setup to replicate what I had before the whole upgrade thing.

After replacing my boot drive and installing Slackware 15, I started in on replicating the prior setup.

With help in another thread I got DVDStyler working. Then this thread got me going on KVM/QEMU to replace VirtualBox. Now I'm just tweaking bits of network behavior.

I am able to access a share on the host with NFS from linux guests. I am currently haggling with Samba. Windows 11 sees the mount but complains I lack permission. Windows 10 and 7 haven't been attempted yet. Windows XP says my host has too many connections.

I'll work on figuring out what I did wrong on the Samba setup, and create a new thread if I need help. I figure that after all the help I have been given on this thread, I should at least keep people updated on the results of their efforts.

Hmm, network is one of the more complex things to get correct. It's often alright to just use the user mode networking, but for any serious tasks a more complex network setup is required, and the proper access rights to do so.

I found a parameter in smb.conf that I didn't remember needing, but it has fixed Windows 11. I expect that 10 and 7 will be OK, XP is still complaining that my host has too many connections. I'll see about getting an NFS client after I get an XP-compatible Firefox in there. I figured out that I can download the FF and create an ISO file, and connect it to the VM. It's the long way around, but I'll only need to do it once...