Virt-Manager isn't going to allow you to start an instance until you enable the default network with virsh. I also feel like it should be mentioned that in order to create / start a network with virsh you need to have linux-headers installed.
--Pyrogon (talk) 17:44 , 30 January 2013 (UTC)Pyrogon
the steps i recommend to follow to ensure virt-manager works properly:
1. libvirtd deamon is up an running with no error in log 2. virtlogd deamon is up and running with no error in log 3. ran the following command once, no error expected. (if network is already active it fails and an error massage apears)
# virsh net-start default
4.at least one virtual network is connected.
--CheesyChocolate (talk) 15:24, 26 April 2023 (UTC)