Check ping

Overview

Sends ICMP ECHO_REQUEST to network hosts using the built-in ping command. Without any parameters it tries to send five packets within one second (so its fast!) and exits after five seconds timeout at the latest. It doesn’t care about round trip times or packet loss as long the host is still reachable in some way. That means 90% packet loss is ok, while 100% are not. Why? If this check is used to test the host-liveliness (which in 99.9% is its use case), mostly all other service checks depend on its result. For that reason it should be as tolerant and reliable as possible and only throw CRIT (equal to DOWN) if the host is definitely not reachable at all.

check_ping from nagios-plugins just prints PING OK - Packet loss = 0%, RTA = 3.79 ms, while this check tells you everything that you are used to if using the ping command directly: PING localhost(localhost (::1)): 5 packets transmitted, 5 received, time 828ms. rtt min/avg/max/mdev = 0.029/0.113/0.189/0.052 ms.

This command works with both IPv4 and IPv6.

The --always-ok parameter is useful for hosts that do not allow ping, but which can still execute check-plugins. The packet loss will be reported, but the state will be OK.

Fact Sheet

Check Plugin Download

https://github.com/Linuxfabrik/monitoring-plugins/tree/main/check-plugins/ping

Check Interval Recommendation

Once a minute

Can be called without parameters

Yes

Compiled for

Linux

Help

usage: ping [-h] [-V] [--count COUNT] [-H HOSTNAME] [--interval INTERVAL]
            [-t DEADLINE]

Sends ICMP ECHO_REQUEST to network hosts using the built-in `ping` command.

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  --count COUNT         Stop after sending count ECHO_REQUEST packets.
                        Default: 5
  -H HOSTNAME, --hostname HOSTNAME
                        The ping destination. Default: 127.0.0.1
  --interval INTERVAL   Wait interval seconds between sending each packet.
                        Default: 0.2
  -t DEADLINE, --timeout DEADLINE
                        Specify a timeout, in seconds, before ping exits
                        regardless of how many packets have been sent or
                        received. Default: 5

Usage Examples

./ping --hostname localhost
./ping --interval=0.2 --count=5 --timeout=5 --hostname localhost

Output:

PING localhost: 5 packets transmitted, 5 received, 0% packet loss, time 829ms. rtt min/avg/max/mdev = 0.036/0.082/0.103/0.023 ms

States

  • CRIT if sending ICMP ECHO_REQUEST to network host fails

  • UNKNOWN if name or service is unknown, out of memory, etc.

  • Otherwise OK

Perfdata / Metrics

Name

Type

Description

checksum_corrupted

Number

Packets with corrupted checksum

duplicates

Number

Duplicate packets. If duplicate packets are received, they are not included in the packet loss calculation, although the round trip time of these packets is used in calculating the minimum/average/maximum/mdev round-trip time numbers.

errors

Number

Packets with errors

packet_loss

Percentage

Packet loss in %

received

Number

Received packets

rtt_avg

Milliseconds

Average round trip time

rtt_max

Milliseconds

Maximum round trip time

rtt_mdev

Milliseconds

Population standard deviation (mdev), essentially an average of how far each ping RTT is from the mean RTT. The higher mdev is, the more variable the RTT is (over time).

rtt_min

Milliseconds

Minimum round trip time

time

Milliseconds

Time

transmitted

Number

Transmitted packets

Troubleshooting

From man ping and related to this check:

When using ping for fault isolation, it should first be run on the
local host, to verify that the local network interface is up and
running. Then, hosts and gateways further and further away should be
“pinged”. Round-trip times and packet loss statistics are computed. If
duplicate packets are received, they are not included in the packet
loss calculation, although the round trip time of these packets is used
in calculating the minimum/average/maximum/mdev round-trip time
numbers.

Population standard deviation (mdev), essentially an average of how far
each ping RTT is from the mean RTT. The higher mdev is, the more
variable the RTT is (over time). With a high RTT variability, you will
have speed issues with bulk transfers (they will take longer than is
strictly speaking necessary, as the variability will eventually cause
the sender to wait for ACKs) and you will have middling to poor VoIP
quality.

Credits, License