What is a MAC address?
Which MAC address does what?
Where do I find my MAC addresses?
What happens if I change my MAC address?
How do I know LV Cable has my correct MAC address?

MAC Address FAQ

1. What is a MAC address?

Every device that connects to a network has a "Media Access Control" (MAC) address. Each MAC address is unique, guaranteeing that no two devices will conflict when accessing the network media (whether that media be cable, wireless, a dial-up connection, or whatever).

A MAC address comprises 12-characters, each in the "hexadecimal" range (0 through 9 and A through F). Decimal points may be inserted every 2 or 4 digits for formatting purposes, but they have no effect on the address.

The Institute of Electrical and Electronic Engineers acts as a world-wide coordinating body that assigns ranges of MAC addresses to manufacturers of network equipment in blocks of 16 million, each identified by the first six characters.

2. Which MAC address does what?

When a computer or router is connected to a cable modem system, there are two MAC addresses involved--that of the modem, and that of the computer, router, or other device to which the modem is connected. These are called the "modem" MAC address and the "host" MAC address, respectively. If you have a computer directly connected to your cable modem, the host MAC address will be set by the NIC card that you are using.

When you connect to the Internet over the LVC system, both MAC addresses are passed on:

Modem MAC Address: The head-end equipment is programmed with the MAC address of each customer. It is this address that makes it possible for the head-end equipment to recognize you as a valid subscriber and provide service with the speed caps associated with your plan.
Host MAC Address: The host MAC address is used in the process of assigning you a "lease" (IP address) when transferring information over the Internet. If you have our Wireless Plan, the host MAC addresses of all your wireless computers may be listed in the access point to ensure that only your computers will be able to have wireless access to your network (this is called "MAC address filtering.")

Note: If your cable modem is connect to a router, the MAC addresses of your computers are not passed on to the head end. Your router will use them to manage its activities, but the router itself furnishes the host MAC address for your cable modem connection.

3. Where do I find my MAC addresses?

Motorola Modem: The modem MAC address is printed on the bottom or back of the modem itself.
Wireless Cards.: The MAC addresses are usually printed on the edge of the card.
Network Interface Cards: You need to read the MAC address with software. Instructions may be found at www-dcn.fnal.gov/DCG-Docs/mac/

4. What happens if I change my MAC addresses?

When you change cable modems, NIC cards (or whole computers), you will replace old MAC addresses with new ones. If you change cable modems, you will no longer be able to access your broadband service--so it is important that you coordinate any such move with Lucas Valley Cable so that we can reprogram your account on the head-end equipment.

When you change routers, the new MAC address will cause a new IP address to be assigned. This can be a problem if you have a Family, Business or Wireless plan because a change in host IP causes you to use the Quality of Service that goes with your plan. For that reason it is important to coordinate router changes with Lucas Valley Cable.

If you have a router, one handy way to get MAC and IP addresses is to log into the router's maintenance screen and check the Local Area Network (LAN). Find the link or button that generates a "DHCP Client Table." You will see the list of computers to which the routers has assigned addresses and might be able to recognize them by the names that you may have given them.

5. How do I know LV Cable has my correct MAC addresses?

If you have reason to believe that our records are wrong with regard to a modem MAC address, you can check the address on the modem against our records by logging into the Support area on the Support Page . There is a form at the bottom of the page that you may use to advise us in the event that the addresses do not match or, if they do, if you suspect that you are not getting the service that you ordered.

Business and Wireless plan customers will also be able to check their host MAC address by logging into the Support area.