A tour of the internals of Weave Net, one of the most popular container networks: design challenges and lessons learned from five years in the wild. Including Kubernetes integration and how CNI was born. Weave Net is written in Go, using many Linux kernel features such as veths, bridges and iptables. Aimed at developers rather than network engineers, Weave Net tries to be self-configuring and find the best available transport between nodes. The control plane operates via gossip, with no central point of control.