The installation works, but I can't connect from 10.0.2.2 with the outside. The network is isolated.
The problems with that wiki page start here: "then run virt-manager to get the friendly GUI to create KVM guest machines"
With the "friendly GUI" it is difficult to describe the steps in a reproducible way. The instructions about qemu etc. (below) are much more friendly than the "friendly GUI", in my opinion.
Right, but the instructions are to verify the network for test deployments that perhaps do not need external connection. Perhaps this should be explicitly mentioned.
Any suggestions to fixing the problem?
But I suspect that you have to enable masquerading on the host. There are some instructions about this at the end of the wiki page.
Try it, but it doesn't work