Get detailed information about an Internet host. Enter an IP address (64.233.167.99), domain name (google.com), hostname (py-in-f99.google.com), or AS-number (AS15169) to get detailed dns information including reverse dns and forwards, whois information, who hosts the machine, and if it's listed in any RBLs (black lists).

Check any Internet host's reachability and how much latency there is in communicating with it from 50 locations worldwide

Ping is commonly used to determine if a given host is 'alive' on the Internet. It will repeatedly send a datagram to a network host to elicit a response from it and show you if, and how long it took to respond.