felixhummel/docker-default-network-limit

The Problem

Check your docker networks:

$ docker network list
NETWORK ID          NAME                DRIVER              SCOPE
c825b3e4e82c        bridge              bridge              local               
f035729e127d        host                host                local               
b93d6694a10e        none                null                local               

Try to spawn 32 new networks from the default pool by running ./create_networks.sh.

You get 29 networks and an error, because the default pool is limited to 32 networks in total.

$ docker network list -q | wc -l
32

The error message is

Error response from daemon: failed to parse pool request for address space "LocalDefault" pool "" subpool "": could not find an available predefined network

Solution

Explicit subnet: See ./subnets.sh (plain docker network create) and docker-compose.yml.

It would be nice if the defaults could be changed, but as far as I can tell, this is not possible yet. See moby/moby#29376 (closed by mistake).