I used nmap to scan all the ports in the hosts in a network by using the command:
$ nmap 172.31.100.0/24
What I found is that it showed the following in the result:
Nmap scan report for 172.31.100.0
Host is up (0.0039s latency).
Not shown: 998 closed ports
PORT STATE SERVICE
23/tcp open telnet
80/tcp filtered http
172.31.100.0 represent? Is it a specific interface or something else?