Both approaches are valid. Just remember this MAC address issue if you ever reset the device to defaults and then have issues with the ISP connection.
If you experience this in the future, you'll have another opportunity to choose to either fix MAC in the device or work with the cable modem to get it to accept the MAC that is presented.
If your problem is solved, please consider marking this topic as [Solved]. See How to mark a topic as [Solved] for a short how-to.
Thanks! 