Is it really a modem, or something else? Please post the model number so we can figure out exactly what you have.

I'm in a different part of the country so neither Verizon FIOS or Charter Spectrum are available to me. From what Google has told me, FIOS is fiber optic so your "modem" would be an Optical Network Terminal. Spectrum appears to be conventional cable service via coaxial cable, I saw that they do offer fiber optic service to business customers. So with Spectrum I think you would use a DOCSIS cable modem.

No matter what kind of service it is, you only get one connection to the internet and that is shared via a router or a combination modem and router in one box.

We really need the model number of what you are calling a modem.