title: What's is ${FLANNEL_SUBNET} and ${FLANNEL_MTU} when Installing a Kubernetes Master Node via Docker?
body: <p>When Installing a Kubernetes Master Node via Docker, docker config bip and mtu for Run flannel.<br>
  --bip=${FLANNEL_SUBNET} --mtu=${FLANNEL_MTU}<br>
  What's are FLANNEL_SUBNET and FLANNEL_MTU variables? How to set ${FLANNEL_SUBNET} and ${FLANNEL_MTU}?</p>