In this chapter, we learnt how Docker networking is powered with docker0 bridge, its troubleshooting issues, and configuration. We also looked at troubleshooting the communication issues between Docker networks and the external network. Following that, we did some deep dive into libnetwork and the CNM and its life cycle. Then, we looked into containers' communication across multiple hosts using different networking options, such as Weave, OVS, Flannel, and Docker's latest overlay network, with comparison, and the troubleshooting issues involved in their configuration.

We saw that Weave creates a virtual network, OVS uses GRE tunneling technology, Flannel provides a separate subnet, and the Docker overlay sets up each host to connect containers on multiple hosts. After that, we looked into Docker network configuration with OVS and troubleshooting the single host and multiple host setup.