这是以前用ASP写的，本想改成ASP.net的给大家，后来想大家能看懂算法就行了。

ip比对的关键是ip地址的线性化

<%

'可以进入的ip

'218.7.44.0 - 218.7.45.253

'61.180.240.0 - 61.180.240.253

'202.118.208.0 - 202.118.223.253

'

'218.7.44.0 3657903103

'218.7.45.253 3657903612

'

'61.180.240.0 1035268095

'61.180.240.253 1035268348

'

'202.118.208.0 3396784127

'202.118.223.253 3396788220

ip=request.servervariables("remote_addr")

sip=split(ip,".")

num=cint(sip(0))*256*256*256+cint(sip(1))*256*256+cint(sip(2))*256+cint(sip(3))-1

response.write(ip)

response.write("
")

if ((num>=3657903103 and num<=3657903612) or (num>=1035268095 and num<=1035268348) or (num>=3396784127 and num<=3396788220)) then

response.write("抱歉，您的ip不合法！")

response.End()

else

response.write("您的ip合法")

end if

%>