A little clarity

Haven't been on this forum in years. Haven't played with my modems in a about 5 years. So Im a little rusty.

Quick question, can you have 2 same MAC's on one node? I cant remember if you can or not and dont feel like blacklisting my modem by trying.

Trying to hardwire my modded modem to my streaming device while the comcrap modem stays connected to my router.

Thanks