If you have a Spectrum-provided all in one device such as the TC8717 (even if you are using it as a modem only and have all routing/wifi turned off if you're doing that on your own), the additional ethernet connectors on the back can be used to get additional IPv4 addresses via DHCP. I have a second network routed through the second jack with a second public IP address.
Just a guess that you are located in upstate NY, where former operator Frontier's CMTS programming allowed modems to be assigned multiple public IPs and open connections instead of using NAT. With the Spectrum takeover those practices are almost over. Don't expect multiple public IP address assignments to continue after the node equipment is upgraded to 21st century and gateway device programming is standardized.