Identify if request is coming from local network (intranet)

Question

I need to identify if a request comes from Internet or Intranet using either client-side or server-side.

The problem I\'m trying to solve is: our web site can be accesse

Answer 1

This is how I would do the ip check:

string ipString = System.Web.HttpContext.Current.Request.UserHostAddress;
byte[] ipBytes = System.Net.IPAddress.Parse(ipString).GetAddressBytes();
int ip = System.BitConverter.ToInt32(ipBytes, 0);

// your network ip range
string ipStringFrom = "192.168.1.0";
byte[] ipBytesFrom = System.Net.IPAddress.Parse(ipStringFrom).GetAddressBytes();
int ipFrom = System.BitConverter.ToInt32(ipBytesFrom, 0);

string ipStringTo = "192.168.1.255";
byte[] ipBytesTo= System.Net.IPAddress.Parse(ipStringTo).GetAddressBytes();
int ipTo = System.BitConverter.ToInt32(ipBytesFrom, 0);

bool clientIsOnLAN = ipFrom >= ip && ip <= ipTo;

If you have multiple subnets, just do the same for them (from, to), then add to the bool condition above. I just realized that, in your case, the above may be an overkill.

Alternatively, for you, it might be as simple as:

bool isOnLAN = System.Web.HttpContext.Current.Request.UserHostAddress.StartsWith("192.168.1.")