title: Changing default subnet for docker custom networks
body: <p>Our internal network has the range 172.20.0.0/16 reserved for internal purposes and docker uses the 172 range by default for its internal networking. I can reset the bridge to live in 192.168 by providing the <code>bip</code> setting to the daemon:</p>
  
  <pre><code>➜  ~ sudo cat /etc/docker/daemon.json
  {
    "bip": "192.168.2.1/24"
  }
  
  ➜  ~ ifconfig                        
  docker0: flags=4099&lt;UP,BROADCAST,MULTICAST&gt;  mtu 1500
      inet 192.168.2.1  netmask 255.255.255.0  broadcast 0.0.0.0
  </code></pre>
  
  <p>However, when creating new custom networks via <code>docker network create</code> or by defining them in the <code>networks</code> sections of the <code>docker-compose.yaml</code> these are still created in 172, thus eventually clashing with <code>172.20</code>:</p>
  
  <pre><code>➜  ~ docker network create foo
  610fd0b7ccde621f87d40f8bcbed1699b22788b70a75223264bb14f7e63f5a87
  ➜  ~ docker network inspect foo | grep Subnet
                  "Subnet": "172.17.0.0/16",
  ➜  ~ docker network create foo1              
  d897eab31b2c558517df7fb096fab4af9a4282c286fc9b6bb022be7382d8b4e7
  ➜  ~ docker network inspect foo1 | grep Subnet
                  "Subnet": "172.18.0.0/16",
  </code></pre>
  
  <p>I understand I can provide the subnet value to <code>docker network create</code>, but I rather want all such subnets created under <code>192.168.*</code>. </p>
  
  <p>How can one configure <code>dockerd</code> to do this automatically?</p>