This message is directed to a Comcast employee that can assist me. Tech support was No help. The tech and supervisor kept telling me they couldn't help me on a private modem. When tech support told me it was NOT possible - I told them to reference a forum where this issue was fixed by a Comcast employee and then I was hung up on.
chrija777, welcome to the forums! I just responded back to your PM regarding the additional IP address. Looking forward to hearing back from you there.