the problem is I cannot even connect locally on the server itself by using localhost/wa, the status bar of the browser shows that it connects to williamtcau.no-ip.org and after a long time, return document not found error.

I am not sure if this could help.
1. From my understanding, if you are running Windows 2003 R2... by default IIS should be version 6.0
2. Two portal aliases should point to the correct same portal, I think you have already done this.
3. Check IIS settings to make sure every request from local network go to correct website. Also check Host Header as well.
4. Some modem routers do not allow you to do this from internal network by default. you can solve this by going to

"C:\WINDOWS\system32\drivers\etc\"  and open file: hosts

and add this below line
127.0.0.1       williamtcau.no-ip.org

save and close
this will make sure that when you request to connect the website "williamtcau.no-ip.org" it will connect direct to "127.0.0.1" which is your localhost.


Hope these help.

 

Good to know that it works for you.

Obviously, the problem you are facing was from your modem router configuration.

I think if you are running this computer for development work and no other computers, you don't have to worry about this as long as your customer can connect your portals without any problem.

But if you want more scalability solution for this, I would recommend one of the following:

1. Configure your modem router to make it works properly.

OR

2. Implement internal DNS, Add (A) record for internal network or any configuration that right for you and point every computer to this DNS server instead of modem router.