Question

I have an IP address in unsigned long format, coding in C++
I have a CIDR notation IP address range such as “10.2.3.98/24”

How do i check if my IP address overlaps with the mentioned range?

Answer 1

This should work if you already know ip addresses as unsigned long and numbers:

bool cidr_overlap(uint32_t ip1, int n1,
                  uint32_t ip2, int n2)
{
    return (ip1 <= (ip2 | ((1ul << (32-n2))-1)))
        || (ip2 <= (ip1 | ((1ul << (32-n1))-1)));
}