DNS and something else, 'handshake' (?) can take seconds to proceed at times. Messages reporting these steps show at the bottom of the screen. For a complex page with many links the process can take several seconds. Sometimes even a simple page fails altogether. Sonic and Ookla's speedtest show normal speed - when I can connect to them. I recently participated in an hour-long online interactive class with no breaks in communication, in contrast to the continual difficulty I have clicking on successive news articles, for example.
Often after a long wait the modem reports 'unable to connect to [central office]' while my EOP connection from the PC and printer, and wireless links from the laptops to the modem, remain connected. Rebooting the modem has seldom helped. In rare instances, likely just luck, a connection was found after the modem had been off for a minute but the same minute reconnect is also the result of simply waiting.
I have service in Sebastopol and another in Sacramento. Both FTTN provided via ATT. Different model modems provided by Sonic at the two locations. Identical DNS problems at both. All my observations point to ATT's DNS servers being flaky.
Both modems require use of ATT's central DNS servers, hard coded into the modem, rather than naming a different DNS server in the modem.
In the past I've had many visits from ATT and Sonic's techs and in both locations have replaced Cat5 between the entry point at the modem after both told me they had eliminated all possibilities, so that house cabling was the only remaining variable. In both locations, each less than 6 ft, the new cable made no difference. If a Sonic tech is reading this, see my multiple tickets before I gave up several months ago.
Any advice, or a workaround?