ICMP ping packet size

[uquerx]

Hello everybody,

From my prometheus server I'm not able to ping the device I wish to monitor with the default icmp packet size (64 bytes) but ok if I force with a ping 32 byte.

Exemple

# ping 10.X.X.200
PING 10.X.X.200 (10.X.X.200) 56(84) bytes of data.
--- 10.X.X.200 ping statistics ---
7 packets transmitted, 0 received, 100% packet loss, time 9ms

but like this

# ping -s 32 10.X.X.200
PING 10.X.X.200 (10.X.X.200) 32(60) bytes of data.
40 bytes from 10.X.X.200: icmp_seq=1 ttl=63 time=1.97 ms
40 bytes from 10.X.X.200: icmp_seq=2 ttl=63 time=1.92 ms
40 bytes from 10.X.X.200: icmp_seq=3 ttl=63 time=1.86 ms
--- 10.X.X.200 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 3ms

Do you know if with blackbox_exporter there is a chance to configure an ICMP ping probe with a 32 Byte packet instead of 64 Bytes???

Host operating system:

Linux 5.4.106-1-pve #1 SMP PVE 5.4.106-1 (Fri, 19 Mar 2021 11:08:47 +0100) x86_64 GNU/Linux

This is my prometheus.yml file:

- job_name: blackbox-ping
    metrics_path: /probe
    params:
      module: [icmp]
    static_configs:
      - targets:
        - 10.XX.XX.200   # <== Put here your targets
    relabel_configs:    # <== This comes from the blackbox exporter README
      - source_labels: [__address__]
        target_label: __param_target
      - source_labels: [__param_target]
        target_label: instance
      - target_label: __address__
        replacement: 127.0.0.1:9115  # Blackbox exporter

[uquerx]

Hello,

Finally I found the solution by myself. You have to use payload_size value when you configure the ICMP probe in your blackbox.yml.
Example for me:

modules:
  ip4_icmp:
    prober: icmp
    icmp:
      preferred_ip_protocol: "ip4"
      payload_size: 32

And voilà