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How does Geo-location from IP work anyway? From my knowledge it's just figuring out the ISP the IP-block is assigned to, and finding out the address of the ISP.

How does Geo-location from IP work anyway? From my knowledge it's just figuring out the ISP the IP-block is assigned to, and finding out the address of the ISP. But technically a computer anywhere in the world can have any IP? Or since I don't know anything about routing: are there routing rules that would think "This is an Indian IP, I'm going to forward this data towards India"?

jaywalk 4y ago
Any computer can't have any IP, but the routing rules have nothing to do with physical location. Routers advertise to their neighbors the IP block(s) that they serve. As a super high level example, your ISP's core router would advertise to other ISP's routers that it serves 10.123.x.x IPs, so any IP address in that block gets sent to that router. Then within your ISP, the router in your area would advertise that it serves 10.123.45.x, so it receives packets for IPs in that more specific block from the core router. So your IP would have to be within the 10.123.45.x block, because that's what the router serving you is assigned.
petercooper 4y ago
I think it goes deeper than that. Even here in the UK with its heavily centralized PoPs it's possible for geolocation tools to narrow a consumer down to a specific town (my cable connection tends to get geolocated to a big town 20 miles from me though) so I assume databases of locations of PoPs are maintained somewhere too.
mulmen 4y ago
Cross reference with billing address? Your ISP knows where you live, and what IP you have. Do you trust them not to sell that data? Any delivery of anything on your phone at least goes to a nearby cell tower but probably exits on your IP from your wifi, and has your address as a requirement. Seems very easy. Uber Eats, Doordash, etc all know the address of your ip as a requirement to perform their services.
Anunayj 4y ago
There isn't a standard way to do this, and all depends on people using random "Geo IP" databases. Most of these databases are made using a variety of sources, though primarily the easiest is to see what ASN the IP address belongs to, and then you just put all those IPs as belonging to that ISPs country. This covers 90% of the domestic users. What ExpressVPN has to do is, simply convince one of these ASNs to allow announcing a IP block from them on BGP, and that will work until some GeoIP database finds out and changes the country for whatever IP block ExpressVPN got. In some cases, traceroutes from different locations around the world can be used to roughly triangulate the location. Though you may find the datacenter to be inside of earth if the IP is actively being used for unicast :)

jaywalk 4y ago

Any computer can't have any IP, but the routing rules have nothing to do with physical location. Routers advertise to their neighbors the IP block(s) that they serve. As a super high level example, your ISP's core router would advertise to other ISP's routers that it serves 10.123.x.x IPs, so any IP address in that block gets sent to that router. Then within your ISP, the router in your area would advertise that it serves 10.123.45.x, so it receives packets for IPs in that more specific block from the core router. So your IP would have to be within the 10.123.45.x block, because that's what the router serving you is assigned.

petercooper 4y ago

I think it goes deeper than that. Even here in the UK with its heavily centralized PoPs it's possible for geolocation tools to narrow a consumer down to a specific town (my cable connection tends to get geolocated to a big town 20 miles from me though) so I assume databases of locations of PoPs are maintained somewhere too.

mulmen 4y ago

Cross reference with billing address? Your ISP knows where you live, and what IP you have. Do you trust them not to sell that data? Any delivery of anything on your phone at least goes to a nearby cell tower but probably exits on your IP from your wifi, and has your address as a requirement. Seems very easy. Uber Eats, Doordash, etc all know the address of your ip as a requirement to perform their services.

Anunayj 4y ago

There isn't a standard way to do this, and all depends on people using random "Geo IP" databases. Most of these databases are made using a variety of sources, though primarily the easiest is to see what ASN the IP address belongs to, and then you just put all those IPs as belonging to that ISPs country. This covers 90% of the domestic users. What ExpressVPN has to do is, simply convince one of these ASNs to allow announcing a IP block from them on BGP, and that will work until some GeoIP database finds out and changes the country for whatever IP block ExpressVPN got. In some cases, traceroutes from different locations around the world can be used to roughly triangulate the location. Though you may find the datacenter to be inside of earth if the IP is actively being used for unicast :)