Host Discovery Without ICMP

Verify a host is up when ICMP echo is blocked. -sn disables port scanning (discovery only).

sudo nmap -sn -PS some_ports DOMAIN     # TCP SYN ping (port 80 default)
sudo nmap -sn -PA some_ports DOMAIN     # TCP ACK ping (port 80 default)
sudo nmap -sn -PY some_ports DOMAIN     # SCTP INIT ping (port 80 default)

UDP ping (ports 31,338 default). A data length of 32 mimics Windows, 56 mimics Linux:

sudo nmap -sn -PU some_ports --data-length 32 DOMAIN

Non-echo ICMP pings — -PP timestamp, -PM address mask:

sudo nmap -sn -PP DOMAIN
sudo nmap -sn -PM DOMAIN

Or just try a TCP connection to a likely port:

telnet DOMAIN some_port
nc DOMAIN some_port