View source for Ping

ping is a tool written by the late Mike Muus to measure latency and round-trip time between two hosts connected by a network. Often it is also used to simply debug if the other host is up.  It works by sending an [[ICMP]] type 8 (request) packet to the remote host which replies with an [[ICMP]] type 0 (reply) packet.  Sometimes there is a [[firewall]] preventing a ping from receiving a reply.

This would look like so:
 $ ping -c 1 www.yashy.com
 PING mail.yashy.com (206.248.137.44): 56 data bytes
 --- mail.yashy.com ping statistics ---
 1 packets transmitted, 0 packets received, 100.0% packet loss

If you're using a packet [[sniffer]] you should see both the request and the reply if things are working unmolested.
 # tcpdump -i [[Variables|rl0]] host gateway.home.lan
 18:13:30.601477 IP laptop.home.lan > gateway.home.lan: ICMP echo request, id 36372, seq 2, length 64
 18:13:30.601773 IP gateway.home.lan > laptop.home.lan: ICMP echo reply, id 36372, seq 2, length 64

One of the original [[DoS]] was a simple ping flood. If you have more bandwidth then your victim, you can do
 # ping -f example.com.
and slow your victim to a grinding halt.

A similar tool to ping would be [[traceroute]].