Boot2docker uses DHCP by default. Most solutions I found simply assign a static address and neglect to disable DHCP. Which led to the machine simply changing its ip address after some time.
This command line should take care of that:
cat <<EOF | docker-machine ssh docker-host sudo tee /var/lib/boot2docker/bootsync.sh > /dev/null kill `more /var/run/udhcpc.eth0.pid` ifconfig eth0 10.0.0.10 netmask 255.255.255.0 broadcast 10.0.0.255 up ip route add default via 10.0.0.1 EOF
After creating that file on the host restart it and regenerate the client certificates:
docker-machine restart docker-host docker-machine env docker-host docker-machine regenerate-certs docker-host