如何在C＃/ asp.net中将IP地址拼接为网络地址？

Question

I'm working on a service desk application that returns a variety of information on the local network of a PC.

What I want to do is take the ip address of the PC - say 10.20.30.1 / 24, and get just the network octets. 10.20.30 in this case. However, even if the network was something like 100.15.1 it would still need to work.

I'd then want to add on different device numbers. For instance, if all the switches in a network fall in the 230 - 235 range by policy, I'd want to be able to cycle through and ping those numbers looking for active switches.

Right now I'm only working with /24 networks.

So far I'm pulling the IP address of the PCs fine, but I'm a little lost on how to proceed.. Should I change the IP into a string and use some kind of regex method to strip the first three octets? That feels a little clunky.

I don't mind reading up on new methods, etc, I'm just looking to get pointed in the right direction, so to speak.

Answer 1

Just

var s = "10.20.30.1 / 24";
s = s.Substring(0, s.LastIndexOf(".")); //"10.20.30"

Answer 2

You should use the IPNetwork2 nuget package that parse ipnetworks.

https://www.nuget.org/packages/IPNetwork2/

https://github.com/lduchosal/ipnetwork

IPNetwork ipnetwork = IPNetwork.Parse("10.20.30.1/24");

Console.WriteLine("Network : {0}", ipnetwork.Network);

Output

Network : 10.20.30.0

Have fun !

Answer 3

Regex methods wont work unless the network addresses are at 8-bit multiples. For a network address of abcd/n, what you need to do is create a bit-mask with n-ones, and then bitwise-and it to the IP address you want to test.

So mask = 0xffffffff << (32-n) to get you the bitmask, and then IPAddress_as_uint && mask to get you the network portion.