ICMP Echo Ping    The  -PE option performs an ICMP (Internet Control Message Protocol) echo ping on the specified system.    Usage syntax: nmap -PE [target]      # nmap -PE 192.168.1.254  Starting Nmap 5.00 ( http://nmap.org ) at 2009-08-16 13:26 CDT  Interesting ports on home (192.168.1.254):  Not shown: 998 closed ports  PORT STATE SERVICE  80/tcp open  443/tcp open  http  https  MAC Address: 00:25:3C:5F:5A:89 (2Wire)  Nmap done: 1 IP address (1 host up) scanned in 1.89 seconds   Performing an ICMP echo ping    The -PE option sends a standard ICMP ping to the target to see if it replies. This type of discovery works best on local networks where ICMP packets can be transmitted with few restrictions. Many internet hosts, however, are configured not respond to  ICMP packets for security reasons.      Note  The -PE option is automatically implied if no other ping options are specified.