"South Park already did it": https://en.wikipedia.org/wiki/Over_Logging

Hah, yeah I did originally think something along those lines, but I wonder if you could actually do it non-comedically (e.g. somehow every node connected to the internet has to all be switched off at the same time and restarted to restore connectivity). Most likely it's already been tried too I guess.

usually, it's a nefarious evil doer that is threatening this action in the movies vs we gotta reboot the city.

there's been reboot the sun plot. there's been reboot the earth's core plot. there's been reboot the machine running the city plot.

I was thinking more along the lines of a rogue self-replicating packet where every last instance of had to die before routers and switches etc. would start working again.