I want to share a solution path to those who experience the following with their wired home internet devices. Spontaneously during the work day a desktop with a wired ethernet connection to the g1100 gateway router suddenly wasn't able to connect to the internet nor any other devices. The network is home to many wireless devices, and a few wired. I had one other computer using a wired connection on this network, and it showed the same issues. Further testing revealed that Fios set-top boxes were also not able to perform network functions, although channel selection using set-top resident settings was still working.
I logged a call with Verizon tech support, and described the symptoms to the agent, who was, by the way, very helpful with Q and A and showed immediate understanding of the issues. The only solutions offered involved either a gateway factory reset, or deliver of a replacement gateway in a couple of days. I went for the latter, figuring that I might be able to figure out the issue within the 2 days time.
Looking at forum posts from others with similar experiences, I noted a response that mentioned the possibility of a LAN loop. This jogged an idea in my head that perhaps one of my wired device's network adapters, or one of the switching hubs through which they're connected might be misbehaving, causing the router to reject all wired connections. The next step was to remove all wired connections from the router, including set-top coax, from the router, power cycle the router, and then test one connection at a time. Sure enough, that was the problem.
Posting this to help others facing a similar issue. It might not fix your problem, but this methodology should help to narrow down the likely cause.