Ping

There are many network utilities that are ready to use out of Linux box. ping is one of them:

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DESCRIPTION
       ping uses the ICMP protocol's mandatory ECHO_REQUEST datagram to elicit
       an  ICMP  ECHO_RESPONSE from a host or gateway.  ECHO_REQUEST datagrams
       (``pings'') have an IP and ICMP header, followed by  a  struct  timeval
       and  then  an  arbitrary  number  of ``pad'' bytes used to fill out the
       packet.
       ping6 can also send Node Information Queries (RFC4620).

pings are ECHO_REQUEST datagrams.

For a quick usage:

% ping localhost
PING localhost (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_req=1 ttl=64 time=0.034 ms
64 bytes from localhost (127.0.0.1): icmp_req=2 ttl=64 time=0.045 ms
64 bytes from localhost (127.0.0.1): icmp_req=3 ttl=64 time=0.039 ms
^C
--- localhost ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
rtt min/avg/max/mdev = 0.034/0.039/0.045/0.006 ms

rrt is the round-trip time in milliseconds. The statistics includes minimum, average, maximum and mean deviation times.

The manual page explains many options. Here are onces I found helpful to me:

ping -D -n -q -c 100 localhost
  • -D: UNIX timestamp + microseconds
  • -n: no lookup symbolic names for host addresses (faster)
  • -c: number of pings to send
  • -q: result only

Ping localhost to verify that the local network interface is up and running:

% ping -d -n -q -c 100 localhost
PING localhost (127.0.0.1) 56(84) bytes of data.

--- localhost ping statistics ---
100 packets transmitted, 100 received, 0% packet loss, time 99005ms
rtt min/avg/max/mdev = 0.029/0.047/0.059/0.007 ms

Ping local gateway, usually router:

% ping -D -n -q -c 100 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.

--- 192.168.1.1 ping statistics ---
100 packets transmitted, 100 received, 0% packet loss, time 98997ms
rtt min/avg/max/mdev = 0.416/0.502/1.448/0.100 ms

If we ping a remote server without using -n option, it will be slower due to the host address lookup:

% ping -c 20 baidu.com
20 packets transmitted, 20 received, 0% packet loss, time 96034ms
rtt min/avg/max/mdev = 46.061/49.096/92.912/10.061 ms

Without lookup:

% ping -c 20 -n baidu.com
20 packets transmitted, 20 received, 0% packet loss, time 19029ms
rtt min/avg/max/mdev = 45.802/46.428/47.391/0.458 ms

Look up the actual IP address of the domain:

% nslookup baidu.com
Server:         127.0.0.1
Address:        127.0.0.1#53

Non-authoritative answer:
Name:   baidu.com
Address: 220.181.111.86
Name:   baidu.com
Address: 220.181.111.85
Name:   baidu.com
Address: 123.125.114.144

We can send pings by using IP address directly, which is almost the same as using -n option. It is faster:

% ping -c 20 220.181.11.86
--- 220.181.111.86 ping statistics ---
20 packets transmitted, 20 received, 0% packet loss, time 19026ms
rtt min/avg/max/mdev = 46.103/53.019/86.077/12.831 ms

But not all servers support ping, pings might be dropped altogether. Also, even a server does support ping, it does not mean that you can browser the website hosted by the server. The port might get blocked, or server is down.

Pinging an IP address is fun, but what is more exciting to actually find out more information about the address, such as the geographical location of the IP. What Is My IP Address is good tool to use.

Next: ping6.