How Does Comcast Check My IP?

Comcast assigns every cable modem an IP address.

Comcast cable's high speed Internet service utilizes Dynamic Host Configuration Protocol (DHCP) servers to assign Internet Protocol, or IP addresses to the cable modems of its clients on its broadband network.

Mac Address

Every device that is connected to the Internet has a unique Media Access Control or MAC address. Comcast keeps a list of it's customers, and the MAC addresses of their cable modems. This ensures only paying customers are able to use the network.

IP Requests

When a cable modem is connected to the Comcast network it requests an IP address from Comcast's DHCP servers. Comcast only assigns the modem an IP address if the modem's MAC address is on the list of provisioned modems assigned to paying customers.

IP Leases

Comcast keeps a log of the date, time and MAC address for every IP request and the length of each lease. If there is ever a request for the owner of an IP address, Comcast is able to cross-reference the IP address to this data to identify the owner of the account.

References

• Comcast: IP Addresses
• Internet Engineering Task Force: Dynamic Host Configuration Protocol
• Internet Engineering Task Force: Internet Protocol