检测IP是否同一网段

<%@LANGUAGE="JavaScript"%>
<%
function ip2hex(ip)
{
var ip4 = ip.split(".");
var p,i;
var hexStr = "0x";
for(i=0; i<ip4.length; i++)
{
p = new Number(ip4[i]);
hexStr += p<16?("0"+p.toString(16)):p.toString(16);
}
return(hexStr);
}

function isSubNetIp(startIp,subCode,hostIp)
{
startIp = ip2hex(startIp);
subCode = ip2hex(subCode);
hostIp = ip2hex(hostIp);
return((startIp&subCode) == (hostIp&subCode));
}
//example:
Response.Write(isSubNetIp("221.209.108.138","255.255.255.0","221.209.108.140"));
%>