Why other computers are inaccessible after installing Apache (httpd) service under the Linux (CentOS) system

Original: The reason why the other computers could not be accessed after installing the Apache (HTTPD) service under the Linux (CentOS) system

today I tried to install the httpd (apache2.4.6) with the Yum command on the virtual machine using the CentOS system, and then access the IP address of this virtual machine under Windows system.

because the previous time has been aware of the iptable limit, so in the thought is because the iptable limit 80 port it!

so on the internet to find the next iptable command, and the TCP port 80 is set to allow any IP access:

It is then accessed under Windows and the Web page is displayed properly.

Why other computers are inaccessible after installing Apache (httpd) service under the Linux (CentOS) system