Links

Host Discovery

ARP Discovery

# arp-scan:
sudo arp-scan -I tap0 <IP>/24
# Nmap:
sudo nmap -n -sn <IP>/24 -PR -oG - | awk '/Up$/{print $2}'

ICMP Discovery

# fping: Ping sweep
fping -a -g <IP>/24 2> /dev/nul
# Nmap: Ping sweep and save to file
nmap -n -sn <IP>/24 -oG - | awk '/Up$/{print $2}' >> nmapresults.txt

Ping and ARP scan (combined)

fping -a -g <IP> 2> /dev/null | sudo nmap -n -sn <IP> -PR -oG - | awk '/Up$/{print $2}' | uniq -u > AliveHosts.txt

TCP SYN Scan

For host discovery such as the command above we should also use non ICMP scanning techniques in the event ICMP is blocked on a host and we miss it. We can use the following command below to perform a TCP scan sweep.
nmap -n -sn -PS <IP>/24

TCP ACK Scan

nmap -n -sn -PA <IP>/24

UDP Ping Scan

Useful for bypassing firewalls that filter TCP traffic and allow UDP traffic. By default a UDP scan will scan ports 40 and 125.
nmap -sn -sU <IP>/24

Reverse DNS Lookup

nmap -R -sL <IP>/24

Additional Nmap Parameters

Parameter
Description
-n
Exclude name resolution
-R
reverse-DNS lookup
-sn
only perform host discovery (No port scan)
-sL
List targets that will be scanned