Ugh, if you're identifying sensors by IP instead of some other ID in the payload, you're doing it wrong. NAT between the sensors and you can throw a wrench into that whole scheme in a hurry.
This is just a smell emanating from another poor design, not a justification for IP spoofing. If you want to spoof addresses, do it in the privacy of your own VPN tunnel between the servers. Don't expose that sickness to the Internet.
You sir are quick to jump to very incorrect conclusions. It's a bad habit and you should abandon it at once.
First, I never said we identified the sensors by IP, but it was important that we record the sensor's IP for diagnostic information.
Second, IP spoofing was not done over the Internet, but rather only between our own servers inside our data center. Obviously doing this over the internet would not only be bad, but also highly unreliable.
Port forwarding on some consumer grade routers work using IP addresses (not MAC addresses). If I assign a computer a static 192.168/16 IP and forward a port to it, I'm doing it wrong?
This is just a smell emanating from another poor design, not a justification for IP spoofing. If you want to spoof addresses, do it in the privacy of your own VPN tunnel between the servers. Don't expose that sickness to the Internet.