>>11282161 (lb)
A few possibilities: they might just take out DNS. If that happens, maybe write down some IP addresses ahead of time. If they blackhole backbone/peering routes, then things might be reachable within ASes but that’s difficult because the AS structure is largely opaque to those using it at the edge. If it’s straight up severed like San Jose fiber was years ago (dry run?), then about all you could do is hook a WiFi AP up to a tethered phone with a linux router doing NAT, but that assumes LTE is on. Or I guess you could find DOCSIS switches and reconfigure them to be openly L2 switched but then you have addressing headaches. No good options.