Scan a whole subnet or IP range with Nmap by providing the '*' wildcard with it.

nmap 192.168.1.*

result:

Starting Nmap 6.40 ( http://nmap.org ) at 2016-07-07 23:41 BST
Nmap scan report for router.asus.com (192.168.1.1)
Host is up (0.016s latency).
Not shown: 544 closed ports, 453 filtered ports
PORT     STATE SERVICE
53/tcp   open  domain
80/tcp   open  http
9998/tcp open  distinct32
 
Nmap scan report for 192.168.1.2
Host is up (0.0081s latency).
Not shown: 987 closed ports
PORT    STATE SERVICE
21/tcp  open  ftp
22/tcp  open  ssh
25/tcp  open  smtp
53/tcp  open  domain
80/tcp  open  http
110/tcp open  pop3
139/tcp open  netbios-ssn
143/tcp open  imap
443/tcp open  https
445/tcp open  microsoft-ds
587/tcp open  submission
993/tcp open  imaps
995/tcp open  pop3s
 
Nmap scan report for peter-laptop-1 (192.168.1.69)
Host is up (0.00028s latency).
Not shown: 997 closed ports
PORT    STATE SERVICE
80/tcp  open  http
139/tcp open  netbios-ssn
445/tcp open  microsoft-ds
 
Nmap scan report for 192.168.1.100
Host is up (0.071s latency).
Not shown: 989 closed ports
PORT     STATE SERVICE
80/tcp   open  http
139/tcp  open  netbios-ssn
443/tcp  open  https
445/tcp  open  microsoft-ds
515/tcp  open  printer
631/tcp  open  ipp
6839/tcp open  unknown
7435/tcp open  unknown
8080/tcp open  http-proxy
9100/tcp open  jetdirect
9220/tcp open  unknown
 
Nmap scan report for android-d8443dafc4d5d365 (192.168.1.141)
Host is up (0.083s latency).
All 1000 scanned ports on android-d8443dafc4d5d365 (192.168.1.141) are closed
 
Nmap scan report for RP-AC52 (192.168.1.169)
Host is up (0.047s latency).
Not shown: 998 closed ports
PORT   STATE SERVICE
53/tcp open  domain
80/tcp open  http
 
Nmap done: 256 IP addresses (6 hosts up) scanned in 77.55 seconds