First, like I remind EVERYONE, you don't have a Motorola Modem, you have a ZOOM modem. Zoom leased, then purchased the name motorola, and applied it to THEIR line of equipment. Arris actually purchased Motorola Mobility, and while they leased the name to Zoom, they kept the equipment hardware/software for themselves.
That being said, when you disconnect, is your modem still connected to Cable, (Check the lights on the front), or does it indicate it's reconnecting.
FYI, the MB8611 is a MODEM, and you have a router connected to IT, that provides wired and wireless internet to your devices.