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.)
Task |
Description |
For Instructions, Go To ... |
---|---|---|
Determine if a host is running. |
Involves pinging the hostname. | |
Determine if a host is losing packets. |
Involves using the -s option of the ping command. |
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 |
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 129.144.50.21: icmp_seq=0. time=80. ms 64 bytes from 129.144.50.21: icmp_seq=1. time=0. ms 64 bytes from 129.144.50.21: icmp_seq=2. time=0. ms 64 bytes from 129.144.50.21: 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".