@gadams999:
Do you have a Comcast provided router or your own? My SMC router is only giving /64 PD's. I think customer routers/modems are getting /56's according to Comcast, but still collecting info.
Any device being used as a MODEM (either leased or owned) can have whatever router is connected request whatever prefix size is available based on your class of service (residential /60 or business /56).
Any device being used as a GATEWAY - a modem and router combined into one unit - will only likely request a /64. If a GATEWAY device is put into BRIDGE MODE (some allow you to do this in the web-based GUI, some require calling Comcast), this essentially makes it function similar to a MODEM, and your own router can request whatever prefix size is available based on your class of service.
Comcast has been moving away from renting regular modems, and mostly rents gateway devices now. This has allowed them to raise their rental fees ("We're renting you more than just a modem now, we're renting you a modem AND router!") as well as have some management control over the router portion.