I have cable outlets in almost every room of the house. My router is in my master bedroom and I route cables to the adjacent room. Right now, I am using a wireless ap to get access to the hsi from living room, kitchen and family room. My question is if there is any way I can use the cable outlet to get hsi instead of pulling more cable etc. Can I plug another modem not that I have another modem to get hsi.
Sometimes, if there are many splits in the lines leading to a given outlet, the modem may go offline periodically because it's not getting enough signal. My advice is to go ahead and try it, and if you have trouble, either move the modem back to the old outlet or call Comcast so they can come out and rework the line leading to the new outlet (you may get charged for this).
Diplexers, spliters, multi switches, a/b switches, ect.. all increase signal loss. Always run quad shielded rg6 straight back to the main junction box, with no breaks inbetween .. with exception to one of those inline grounding conectors, always ground your coax.