Docker currently allows creating a network called "default", but should not, because "default" is a reserved name (see #19421), and a network called "default" is not usable after creating;
$ docker network create default
5c34b64abce1ce65b280f7cc008bb2eae4bbbf036046b87e8dd4ad215923c4e9
$ docker run --net=default -itd busybox sh
9abd4f4e6610da0a2870c661b9c48d6d55fb5a35efefbf349a9ae5bbdf975c7d
# The container is actually connected to the "bridge" network, which is the "default"
$ docker inspect --format='{{json .NetworkSettings.Networks}}' 9abd4f4e6610da0a2870c661b9c48d6d55fb5a35efefbf349a9ae5bbdf975c7d
{"bridge":{"IPAMConfig":null,"Links":null,"Aliases":null,"NetworkID":"b41125b6469d76594cbea321e77438ab42dc4881b0f0d9fa8cb8a9163396ec3a","EndpointID":"4eda38a6fe1ffa5f259e6ff48e30b353c84d2c572b9e6e2115c4be15e21ca23d","Gateway":"172.17.0.1","IPAddress":"172.17.0.4","IPPrefixLen":16,"IPv6Gateway":"","GlobalIPv6Address":"","GlobalIPv6PrefixLen":0,"MacAddress":"02:42:ac:11:00:04"}}
Docker currently allows creating a network called "default", but should not, because "default" is a reserved name (see #19421), and a network called "default" is not usable after creating;