Machine: Error con la comprobación previa a la creación: ... no existe tal host

Cuando ejecuto este comando docker-machine create --driver virtualbox default obtengo este error:

Running pre-create checks...
(default) No default Boot2Docker ISO found locally, downloading the latest release...
Error with pre-create check: "Get https://api.github.com/repos/boot2docker/boot2docker/releases/latest: dial tcp: lookup api.github.com on 192.168.0.1:53: no such host"

Además, cuando hago doble clic en docker quickstart terminal , obtengo el siguiente error:

bash --login '/Applications/Docker/Docker Quickstart Terminal.app/Contents/Resources/Scripts/start.sh'
Running pre-create checks...
(default) No default Boot2Docker ISO found locally, downloading the latest release...
(default) Latest release for github.com/boot2docker/boot2docker is v1.10.3
(default) Downloading /Users/mz/.docker/machine/cache/boot2docker.iso from https://github.com/boot2docker/boot2docker/releases/download/v1.10.3/boot2docker.iso...
Error with pre-create check: "Get https://github.com/boot2docker/boot2docker/releases/download/v1.10.3/boot2docker.iso: dial tcp: lookup github.com on 192.168.0.1:53: no such host"
Host does not exist: "default"
Regenerate TLS machine certs?  Warning: this is irreversible. (y/n): Regenerating TLS certificates
Host does not exist: "default"
Host does not exist: "default"


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                  ## ## ##        ==
               ## ## ## ## ##    ===
           /"""""""""""""""""\___/ ===
      ~~~ {~~ ~~~~ ~~~ ~~~~ ~~~ ~ /  ===- ~~~
           \______ o           __/
             \    \         __/
              \____\_______/


Host does not exist: "default"
docker is configured to use the default machine with IP
For help getting started, check out the docs at https://docs.docker.com

Estoy en MAC OS X El Capitan v10.11.3
La versión de mi máquina Docker es: 0.6.0, build e27fb87

Información adicional:

Cuando intento hacer ping a cualquier servidor, obtengo esto:

❯ ping google.com
PING google.com (216.58.211.78): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
Request timeout for icmp_seq 2
Request timeout for icmp_seq 3
^C
--- google.com ping statistics ---
5 packets transmitted, 0 packets received, 100.0% packet loss

Pero todas las demás herramientas (cURL, NPM, Bower, Composer, ...) funcionan bien.