Docker won't create a bridge network without being given an explicit subnet

The problem

The problem is that this happens:

$ docker network create  alpine4
Error response from daemon: could not find an available, non-overlapping IPv4 address pool among the defaults to assign to the network

Notwithstanding that I have no non-builtin docker networks created.

The logs suggest that these network ranges are being attempted:

```
DEBU[2018-08-08T17:21:00.877120275Z] ReleasePool(LocalDefault/192.168.240.0/20)
DEBU[2018-08-08T17:21:00.877135316Z] ReleasePool(LocalDefault/192.168.224.0/20)
DEBU[2018-08-08T17:21:00.877162150Z] ReleasePool(LocalDefault/192.168.208.0/20)
DEBU[2018-08-08T17:21:00.877170059Z] ReleasePool(LocalDefault/192.168.192.0/20)
DEBU[2018-08-08T17:21:00.877176154Z] ReleasePool(LocalDefault/192.168.176.0/20)
DEBU[2018-08-08T17:21:00.877198642Z] ReleasePool(LocalDefault/192.168.160.0/20)
DEBU[2018-08-08T17:21:00.877204723Z] ReleasePool(LocalDefault/192.168.144.0/20)
DEBU[2018-08-08T17:21:00.877212452Z] ReleasePool(LocalDefault/192.168.128.0/20)
DEBU[2018-08-08T17:21:00.877220350Z] ReleasePool(LocalDefault/192.168.112.0/20)
DEBU[2018-08-08T17:21:00.877232829Z] ReleasePool(LocalDefault/192.168.96.0/20)
DEBU[2018-08-08T17:21:00.877243072Z] ReleasePool(LocalDefault/192.168.80.0/20)
DEBU[2018-08-08T17:21:00.877253643Z] ReleasePool(LocalDefault/192.168.64.0/20)
DEBU[2018-08-08T17:21:00.877264171Z] ReleasePool(LocalDefault/192.168.48.0/20)
DEBU[2018-08-08T17:21:00.877274553Z] ReleasePool(LocalDefault/192.168.32.0/20)
DEBU[2018-08-08T17:21:00.877284675Z] ReleasePool(LocalDefault/192.168.16.0/20)
DEBU[2018-08-08T17:21:00.877296023Z] ReleasePool(LocalDefault/192.168.0.0/20)
DEBU[2018-08-08T17:21:00.877307062Z] ReleasePool(LocalDefault/172.31.0.0/16)
DEBU[2018-08-08T17:21:00.877322208Z] ReleasePool(LocalDefault/172.30.0.0/16)
DEBU[2018-08-08T17:21:00.877333550Z] ReleasePool(LocalDefault/172.29.0.0/16)
DEBU[2018-08-08T17:21:00.877339489Z] ReleasePool(LocalDefaul

Do you need to run it beside a VPN "OpenVPN service" ?

I think using below would solve the issue for clearing any unused networks by at least 1 container.

$ docker network prune

StackExchange DevOps Q#4723, answer score: 2