ping

by Chris Kranz on Jul.07, 2009, under Manual Pages

NAME

ping – send ICMP ECHO_REQUEST packets to network hosts

SYNOPSIS

ping [ -rv ] host [ count ]

ping -s [ -Rrv ] host [ packetsize ]

ping uses the ICMP protocol’s mandatory ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE from the specified host or gateway. ECHO_REQUEST datagrams have an IP and ICMP header, followed by a struct timeval and then an arbitrary number of bytes used to fill out the packet. If host responds, ping prints "host is alive." Otherwise, ping will resend the ECHO_REQUEST once a second. If the host does not respond after count retries (default value is 20), ping will print "no answer from host." If the host is specified as a symbolic name and the system is unable to resolve this name to an IP address, ping will print "unknown host host.”

When the -s flag is specified, ping sends one datagram per second and prints one line of output for every ECHO_RESPONSE that it receives. ping computes the roundtrip times and packet loss statistics. When the command is terminated with a ^C, the summary statistics is displayed. The default packetsize is 56, which translates into 64 ICMP bytes when combined with the 8 bytes of ICMP header.

OPTIONS

-R: Record route. Includes the RECORD_ROUTE option in the ECHO_REQUEST packet and displays the route buffer on returned packets. Note that the IP header is only large enough for nine such routes. Many hosts ignore or discard this option. The -R option is ignored without the -s option.

-r: Bypass the normal routing tables and send directly to a host on an attached network. If the host is not on a directly-attached network, an error is returned.