More Work on KVM - Network Configuration

Been a while since I have posted anything on here. I'll do a few updates.

One of the projects I have been working on is the transition from Virtual Box (which I run on a Windows 10 laptop) and ESXi (which we used to run on large servers) to KVM.

What I have been doing is installing an entire network on a KVM host - with different CentOS 7 virtual machines.

Initially when I did this, I put each one of these on their own subnet (default network). Then - when one of the VMs needed a static IP, I learned how to use the virsh commands to edit the xml file for the default network and insert DHCP ranges, and - of these DHCP ranges - lock a specific IP to a specific  host / MAC.

What I really meant to do, was to go back and reconfigure the network to resemble the Virtual Switch mechanism that ESXi provides through the user interface. But I could not - easily - figure out how to do this.

Later, a young greenhorn developer mentioned to me that the "Connection Details" tab in the Virt-Manager GUI would allow you to add/remove and start/stop various networks. And in exploring this, I learned that you can create Routed networks, NAT networks, and custom versions of these. You can also create internal networks.

It appears that you can "enable static routes" on both the NAT and Routed networks - a little confusing but made sense once you started trying to interact between VMs. I had some issues getting NAT networks to interface with Routed Networks until I wised up and, for the VM that needed internet access, created two network interfaces on that VM; one using a NAT network (external internet) and one using Routed (for internal network that could interface with other Routed VMs).

With that I was able to create 7-8 VMs that could interface with one another, and one of those VMs could get out to the internet as required.

There might be more sophisticated things you can do, but I think if you understand the types of networks and how to properly configure them, you should pretty much be where you want to be. I might need to read up on more advanced aspects of KVM but I think I'm good for now.