Preface Achieving intercommunication between containers on multiple Docker servers is a challenging problem. If you build your own overlay network, you need to set up services like etcd on one server. But if the server hosting etcd crashes, the entire network goes down. The cheap VPS I use occasionally experiences network interruptions, and I often accidentally crash servers myself, so this approach isn't feasible for me. Docker also has other commercial overlay networking solutions like Weave, but for individual users, these solutions are too expensive (I'm just experimenting for fun), so they're not considered either. In these network architectures, central servers like etcd or Weave record which server each container is on and its internal IP, allowing DNS resolution to any container....

IPv4 is currently the most widely supported network protocol, where computers are identified by IP addresses. Theoretically, it can accommodate up to 2 32 2^{32} 2 32 network devices (IPv4: 8 hexadecimal digits). Unfortunately, these addresses have been exhausted, and it's truly a mystery how major ISPs allocate limited IP addresses to an infinite number of computers. IPv6 is far more impressive, with each address containing 32 hexadecimal digits, allowing for 2 128 2^{128} 2 128 network devices. These IP addresses will be more than sufficient before humanity perishes due to Earth's inability to sustain us. This protocol is championed by major internet companies including Google, DNSPod, and others. However, currently in China, IPv6 seems to be used only in universities,...