It came up the power connection and the copper phone connection. The modem/router/switch fried, then it spread out though the twisted pair Ethernet and fried every interface connected to the network.
These days I use WiFi unless I really need low latency / high reliability in a particular location. Optical would be nice, but WiFi is the poor man's lightning safe network.
And then standard power isolation and surge protection will handle all the power connections.
I've yet to loose equipment to lightning from the power cables but I literally can't count the amount of equipment that has been killed by lightning striking a copper data line and then surging through my network.
What’s the best way to implement power isolation and surge protection?
Something as simple and cheap as this would do:
https://www.tp-link.com/us/business-networking/accessory/mc2...
It was a lot easier to run a pair of fiber-optic cables there than it would've been to do the same with cat6. Also I got to play around with fiber for the first time.
Never thought of isolating my modem from the rest of my gear though, I need to look into that.
And then you can put surge equipment on any other incoming wires.
With only one connection (power or phone) the whole device tends swing at the same potential. Damage can occur if it arcs to ground, but that's less likely as in a device the isolation to ground is typically higher than between the power and data parts of a circuit. (Extra bad news if the arc to ground happens via a person.)
Incidentally, if a lightning strike is nearby a typical consumer surge protector will improve the odds but probably won't prevent damage.
A few months later we got struck again. The router survived but the building caught fire.
Now that I'm older I just accept the risk that "sometimes nature hates you". Instead of jumping through hoops to protect my gear from nature I just set aside money to replace anything I can't afford to lose.
Life's too short to play tug of war with the planet and I'd rather set aside $50/month to pay for replacements when I need them.
When it came back, that modem still worked, but it was stuff "off the hook" forever. I had to unplug/replug it every time I wanted to dial out, and the phone line was permanently busy.