Let me add some nuance here: We have the "business" offering from Comcast. It was the only offering that had 100MBit/s when we signed up. With the "business" offering, you are forced to use the "business" modem.
The modem is made by SMC. It is a full firewall/gateway. Unfortunately, the software on it is not very stable. For about 4-5 months, we worked with Comcast customer support to resolve this. They tried many different things to fix the issue, without success. My conclusion was that the software on the SMC modem just crashes once a day or so, and then hangs.
Eventually, I convinced them to let us use the "simple" residential Motorola modem. That has worked much better. It still crashes every 1-2 weeks, but that's almost acceptable.
The modem is made by SMC. It is a full firewall/gateway. Unfortunately, the software on it is not very stable. For about 4-5 months, we worked with Comcast customer support to resolve this. They tried many different things to fix the issue, without success. My conclusion was that the software on the SMC modem just crashes once a day or so, and then hangs.
Eventually, I convinced them to let us use the "simple" residential Motorola modem. That has worked much better. It still crashes every 1-2 weeks, but that's almost acceptable.