System Administration Guide, Volume 3

ping Command

Use the ping command to find out whether there is IP connectivity to a particular host. The basic syntax is:

/usr/sbin/ping host [timeout]

where host is the host name of the machine in question. The optional timeout argument indicates the time in seconds for ping to keep trying to reach the machine--20 seconds by default. The ping(1M) man page describes additional syntaxes and options.

When you run ping, the ICMP protocol sends a datagram to the host you specify, asking for a response. (ICMP is the protocol responsible for error handling on a TCP/IP network. See "ICMP Protocol" for details.)

ping Command Task Map

Table 6-6 ping Command Task Map



For Instructions, Go To ... 

Determine if a host is running. 

Involves pinging the hostname. 

"Network Databases and nsswitch.conf File"

Determine if a host is losing packets. 

Involves using the -s option of the ping command.

"How Name Services Affect Network Databases"

How to Determine if a Host Is Running

    On the command line, type the following command.

    % ping hostname

    If host hostname is up, this message is displayed:

    hostname is alive

    This indicates that hostname responded to the ICMP request. However, if hostname is down or cannot receive the ICMP packets, you receive the following response from ping:

    no answer from hostname

How to Determine if a Host Is Losing Packets

If you suspect that a machine might be losing packets even though it is running, you can use the s option of ping to try to detect the problem.

    On the command line, type the following command.

    % ping -s hostname

ping continually sends packets to hostname until you send an interrupt character or a timeout occurs. The responses on your screen will resemble:

PING elvis: 56 data bytes
64 bytes from icmp_seq=0. time=80. ms
64 bytes from icmp_seq=1. time=0. ms
64 bytes from icmp_seq=2. time=0. ms
64 bytes from icmp_seq=3. time=0. ms
----elvis PING Statistics----
4 packets transmitted, 4 packets received, 0% packet loss
round-trip (ms) min/avg/max = 0/20/80   

The packet-loss statistic indicates whether the host has dropped packets.

If ping fails, check the status of the network reported by ifconfig and netstat, as described in "ifconfig Command" and "netstat Command".