Ping is one of the most commonly used networking commands in Linux and other operating systems.
Ping is mainly used to check if a remote host is reachable or not. The remote host could be a web server, your router or a system on your local network.
How does ping work? It actually sends small ICMP packets to the remote host and waits for the response. If the host is up, you should see a response.
It’s like the sonar technology used in submarines. The submarines send pulses of audio signal and wait for the echo to return.
So, how do you use Ping in Linux? What are different Ping command options? Let me show you some of the common usages of the Ping command.
Did you know? Ping command is correctly written as PING and it stands for Packet Internet Groper.
Using ping command in Linux
You can use ping command with either the IP address or the hostname/URL.
Suppose I ping Google. It will send ICMP packets of size 56 bytes to google.com.
ping google.com PING google.com (220.127.116.11) 56(84) bytes of data. 64 bytes from 18.104.22.168 (22.214.171.124): icmp_seq=1 ttl=42 time=325 ms 64 bytes from 126.96.36.199 (188.8.131.52): icmp_seq=2 ttl=42 time=387 ms 64 bytes from 184.108.40.206 (220.127.116.11): icmp_seq=3 ttl=42 time=319 ms 64 bytes from 18.104.22.168 (22.214.171.124): icmp_seq=4 ttl=42 time=321 ms ^C --- google.com ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3002ms rtt min/avg/max/mdev = 319.697/338.496/387.785/28.527 ms
You have to manually stop the ping command else it will keep on running. You can use the Ctrl+C terminal shortcut to stop the ping command in Linux, as I did in the above example.
When you stop the ping command, it presents you with a summary of the transmission. You can see stats like the number of ICMP packets transmitted, received packets, lost packets etc.
Now that you know how to ping in Linux, let’s see some of the other ping command options.
Send only N number of packets
If you don’t want the ping command to run forever without manually stopping it, you can use the -c option.
With this, you can specify the number of packets the ping command should send before stopping automatically.
ping -c 2 126.96.36.199
PING 188.8.131.52 (184.108.40.206) 56(84) bytes of data.
64 bytes from 220.127.116.11: icmp_seq=1 ttl=50 time=315 ms
64 bytes from 18.104.22.168: icmp_seq=2 ttl=50 time=423 ms
--- 22.214.171.124 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 315.208/369.190/423.172/53.982 ms
Send ping only for a limited time
Apart from setting the number of packets to send, you can also set for how long the packets will be sent.
For example, if you want to send ping packets for only 5 seconds, you can use it like this:
ping -w 5 google.com
PING google.com (126.96.36.199) 56(84) bytes of data.
64 bytes from yx-in-f138.1e100.net (188.8.131.52): icmp_seq=1 ttl=40 time=407 ms
64 bytes from yx-in-f138.1e100.net (184.108.40.206): icmp_seq=2 ttl=40 time=320 ms
64 bytes from yx-in-f138.1e100.net (220.127.116.11): icmp_seq=3 ttl=40 time=323 ms
64 bytes from yx-in-f138.1e100.net (18.104.22.168): icmp_seq=4 ttl=40 time=472 ms
64 bytes from yx-in-f138.1e100.net (22.214.171.124): icmp_seq=5 ttl=40 time=406 ms
--- google.com ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4002ms
rtt min/avg/max/mdev = 320.634/385.993/472.056/57.309 ms
Change the time interval between two pings
By default, ping sends the packets at an interval of one second. You can change this time interval with the -i option.
To send the ICMP packets with an interval of 3 seconds, you can use Ping command like this:
ping -i 3 126.96.36.199
You can decrease the time interval between pings as well.
ping -i 0.5 188.8.131.52
However, if you try to decrease the time interval below 0.2 seconds (200 ms), you’ll see an error:
ping -i 0.1 184.108.40.206 PING 220.127.116.11 (18.104.22.168) 56(84) bytes of data. ping: cannot flood; minimal interval allowed for user is 200ms
Don’t worry. You can still ping with an interval less than 200 ms. But to do that, you need to use the ping with root privileges.
sudo ping -i 0.1 22.214.171.124 PING 126.96.36.199 (188.8.131.52) 56(84) bytes of data. 64 bytes from 184.108.40.206: icmp_seq=1 ttl=49 time=470 ms 64 bytes from 220.127.116.11: icmp_seq=2 ttl=49 time=372 ms
Change the packet size
The default ICMP packet size sent by Ping is 56 bytes. This can be changed as well with the help of -s command.
ping -s 100 18.104.22.168
PING 22.214.171.124 (126.96.36.199) 100(128) bytes of data.
108 bytes from 188.8.131.52: icmp_seq=1 ttl=49 time=234 ms
108 bytes from 184.108.40.206: icmp_seq=2 ttl=49 time=257 ms
108 bytes from 220.127.116.11: icmp_seq=3 ttl=49 time=280 ms
--- 18.104.22.168 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 234.208/257.352/280.424/18.867 ms
DoS attack with Ping flooding aka Ping of Death
One of the simplest DoS attack is the Ping of Death. In this kind of attack, the attacker sends a large number of ping request in a very short span of time. If the server is not well configured, it will crumble in handling the ping request and the website will go down.
The ping command has built-in ‘feature’ for this. It’s called ping flooding and it can be achieved with the -f option. You’ll need sudo rights to run this option with zero interval.
sudo ping -f google.com
PING google.com (22.214.171.124) 56(84) bytes of data.
--- google.com ping statistics ---
1436 packets transmitted, 1413 received, 1% packet loss, time 22837ms
rtt min/avg/max/mdev = 313.887/326.102/388.178/7.464 ms, pipe 26, ipg/ewma 15.914/323.456 ms
When you run this command, you’ll see some dots appearing and disappearing in the output. Every single ‘.’ denotes a request whereas the reply is a backspace (this is why dots disappear).
This flood ping option is useful in testing the load capacity of a server.
Bonus Tip: Send audible pings
You can send audible pings with -a option. With this, you’ll hear a beep for every successful ping.
ping -a google.com
Note that not all Linux distributions are configured to make the beep noise. I tested it on Ubuntu 18.04 and I could hear the beep.
Troubleshooting Ping command
So far what we have seen is the successful examples of the ping command. But that won’t happen all the time. Let’s see some of the common errors you may see and understand the reason for those errors.
No reply for ping
You might notice that certain hosts do not reply to the ping request. It seems like the ping command has hanged because there is no response. The command just stays there, it doesn’t even times out.
If you terminate the ping command, you’ll see some strange statistics.
PING intel.com (126.96.36.199) 56(84) bytes of data.
--- intel.com ping statistics ---
100 packets transmitted, 0 received, 100% packet loss, time 101362m
As you can see, 100 packets were transmitted but no response was received for any of them.
It’s most likely because some servers discard the ICMP packets. This is a security measure to avoid ping flooding.
Destination host unreachable
This error can occurred because of one of the two reasons:
- Either the local system has no route to the remote host
- or the end point router has no route to the remote host
If you only see the ‘destination host unreachable’ error, this means your system couldn’t find a route to the remote host.
On the other hand, if you see the error in the “Reply from <IP>” part of the reply, it means that the packet was sent outside of your network but it couldn’t reach the destination.
Some times servers also block the ICMP traffic that could show this error.
Request times out
This error means that the packets reached the remote server but the reply could not reach your system. The issue could be lost packets or routing error.
Ready to Ping?
I hope this tutorial helped you in understanding the Linux ping command better.
If you have questions or suggestions, please leave a message in the comment section.