How do IP Addresses Relate to Countries?

Question

I have a general question about IP Addresses. I am not sure if this question is better suited for another S/O Network (like Server Fault), but I thought I'd ask it here.

I want to try to hone in on the relationship between an IP Address and a Country. Is it fair or accurate to say that an IP Address like 100.*.*.* relates to ISPs in the US solely or is it possible that one of the octets with the 100.*.*.* range gets assigned to other Countries?

I am looking for a way to relate IP Address ranges, at their highest level, to Countries on a one-for-one basis.

Thanks.

Answer 1

I don't think there's an explicit rule for that. Check here.

Answer 2

Strictly-speaking, it is my understanding that location roughly correlates with location via IPv4 address blocks. There's a Wikipedia reference for these here.

However, more often than not this isn't particularly accurate - from personal experience relying on these results in more false results than positive. Part of the problem is that these addresses tend to shift with time and use.

MaxMind offer a free geoIP database called GeoLite 2 (link here) which I've used on a few occasions to detect an IP's origin country with a really high success rate, you just have to make sure that you update the database fairly regularly to keep up-to-date.