If you want to get fun with it you can actually fit the entire IP range in a single 32 bit value. On the internet networks larger than /24s aren't considered valid advertisements so you only need to store 3 bytes (the first 24 bits) of the address to hold the start. If you store than in a uint32 you can use the remaining 8 bits to hold the netmask (you don't actually need all of them but it keeps things byte aligned), which lets you dynamically calculate the end address in just a few CPU cycles. The search still occurs on the base address portion so you don't ever have to calculate the end address until you've already found the right base address.