Apache fails to work when IP address is entered in browser

[tcnm]

I installed and started apache 2.2.31 on Linux Ubuntu 15.10. When i enter my loopback id (127.0.0.1) in my browser, the correct message ("It works") appears, but, when i enter my site ip address (71.187.235.187) in the browser, I receive the message: "Firefox can't establish a connection to the server at 71.187.235.187."
Note that the directive "Listen" is set to 80.

The following commands and responses may be relevant:

root@pegasus:/proc# nc -zv 127.0.0.1 80 // Trying to access the loopback ID
Connection to 127.0.0.1 80 port [tcp/http] succeeded!
root@pegasus:/proc# nc -zv 71.187.235.187 80 // Trying to access the site ID
nc: connect to 71.187.235.187 port 80 (tcp) failed: No route to host

[Nobbie]

root@pegasus:/proc# nc -zv 71.187.235.187 80 // Trying to access the site ID
nc: connect to 71.187.235.187 port 80 (tcp) failed: No route to host

This means, that even TCPIP cannot find your IP. It is not an Apache problem, maybe a firewall problem or anything else.