help: why can not get the Request.ServerVariables("LOGON_USER") ?

[step]

I'm a winnt workstation user, I can get these value :

Request.ServerVariables("REMOTE_HOST")
Request.ServerVariables("SERVER_PORT")
Request.ServerVariables("LOCAL_ADDR")

but I can not get this value
Request.ServerVariables("LOGON_USER")
It's return the blank string ""

why?
the problem with my asp sourcecode, or iis? how to fix?
thanks!

[cpplus]

这个是匿名访问的时候没有显示的，如果你把IIS配置成不可以匿名访问的，就会显示你登录的用户名信息喽~~~~

[step]

Thanks you very much~~
But I can not find the corresponding configuration : (
please tell me more detail steps.
55

[step]

ok. I found it. Now it's correct. thanks~