"not yet ready SSH"

[pixel fairy]

host: ubuntu 16.04 (got the same issue on 18.04)

vagrant: 2.1.2

provider: vagrant-libvirt

box: generic/ubuntu1804

$ vagrant ssh web
The provider for this Vagrant-managed machine is reporting that it
is not yet ready for SSH. Depending on your provider this can carry
different meanings. Make sure your machine is created and running and
try again. Additionally, check the output of `vagrant status` to verify
that the machine is in the state that you expect. If you continue to
get this error message, please view the documentation for the provider
you're using.

$ vagrant ssh prom
Last login: Thu Aug  2 13:22:47 2018 from 192.168.121.1
vagrant@prom:~$ exit

works with generic/ubuntu1604, so maybe netplan related? no commits in vagrant-libvirt 

about this. 'vagrant ssh web' is reliable in not working. prom seems random.

ENV['VAGRANT_NO_PARALLEL'] = 'yes'

lan = "10.45.14."

Vagrant.configure("2") do |config|
  config.vm.box = "generic/ubuntu1804"
  config.vm.provision "shell", inline: "apt-get -y install python aptitude"
  config.vm.synced_folder ".", "/vagrant", disabled: true

  config.vm.define "web" do |w|
    w.vm.hostname = "web"
    w.vm.network "private_network", ip: lan + "10"
    # w.vm.provision "ansible", playbook: "web.yml"
  end

  config.vm.define "prom" do |p|
    p.vm.hostname = "prom"
    p.vm.network "private_network", ip: lan + "11"
    # p.vm.provision "ansible", playbook: "prom.yml"
  end

end