title: Docker ip of "default" machine
body: <p>I have a few quick, maybe stupid question about docker, when you start it you get the ip of the default machine what is 192.168.99.100 the first time you install it. 
  But I removed it and installed it again and now its 192.168.99.101. 
  What happend to the first ip and can I change the 192.168.99.101 to 192.168.99.100 again?
  I used the docker-toolbox to install docker!
  Thanks!</p>