: For standard Gigabit Ethernet, Phantom hardware is traditionally assigned to the 100.100.x.x IP range .

There is a second, legitimate occurrence of "100.100" that is not a speed at all. The IP range is reserved for specific VPN protocols (like WireGuard or legacy Cisco VPNs). Occasionally, a misconfigured speed testing tool will attempt to resolve a hostname to 100.100.x.x and mislabel the latency as "Speed 100.100." If you see this, you are looking at an IP address, not bandwidth.

We are currently seeing a "reverse nostalgia" where developers create terminal applications that fake the look for aesthetic purposes—a steampunk approach to networking. But functionally, if you see it, take it seriously: you have either a broken wire, a legacy device, or a very lazy software engineer.