Charter Filters MAC Addresses

A couple of days ago I noticed that my internet was no longer working. I tried to ping 4.2.2.2 with no avail. My network setup consists of a Motorola Surfboard Cable Modem and a Netgear WNR3500L Wireless-N router. I connected my laptop directly to the cable modem and it worked perfectly. I thought that perhaps it was just a power-cycle issue, so I connected the router back to the cable modem and rebooted both. Still, no internet access from the wireless network.

I did a little more digging and found that the cable modem wasn’t assigning the wireless router an IP address, yet if I plugged my laptop directly in to the modem, DHCP worked flawlessly. It then dawned on me that perhaps Charter was doing some type of MAC address filtering to determine which devices to authorize DHCP to use.

MAC (media access control) addresses are the physical address of network cards, both wired and wireless. The first three octets of the MAC address specify the manufacturer of the network card. This allows Charter to differentiate between a wireless router and a laptop computer.

If you are having this issue, there is an easy fix. First, determine the MAC address of your wired connection. If you are on a Windows machine, open a command prompt and type “ipconfig /all”. You will get the following prompt:

The MAC address is the line that says “Physical Address.”

If you are on an Apple/Mac computer, open a terminal window and type “ifconfig”. The local wired connection is en0. The MAC address is the field that says “ether”:

Next, log on to your router and determine where you can set the MAC address, it will look something like this:

Input your physical MAC address and apply your settings. After that, you should be able to obtain an IP.

The only reason I suspect Charter does this is to force you to buy their “Wireless” bundle.