Explanation:
The docker_gwbridge is a local bridge network which is automatically created by Docker in two different circumstances: When you initialize or join a swarm, Docker creates the docker_gwbridge network and uses it for communication among swarm nodes on different hosts. When none of a container’s networks can provide external connectivity, Docker connects the container to the docker_gwbridge network in addition to the container’s other networks, so that the container can connect to external networks or other swarm nodes.
Reference:
https://docs.docker.com/engine/userguide/networking/#the-docker_gwb…