Other | Network

fping is a command line tool to send ICMP (Internet Control Message Protocol) echo requests to network hosts, similar to ping, but performing much better when pinging multiple hosts. The Netdata Agent utilizes fping to monitor latency, packet loss, uptime and reachability of any number of network endpoints.

The fping_host_reachable alert in the Netdata Agent checks the reachability of a network host (0: unreachable, 1: reachable). Receiving a critical alert indicates that your endpoints are unreachable. It is likely that the host is down or your system is experiencing networking issues.


Check network connectivity

Verify that your system has access to the particular endpoint. Check for basic connectivity to known hosts from both your host and the endpoint.

DNS settings

If you are using DNS resolution to check your endpoint, you should always consider check your DNS settings. To troubleshoot this issue, verify that your DNS can resolve your endpoints.

  1. Check your current DNS (for example in linux you can use the host command):

    root@netdata # host -v <your_endpoint>
  2. If the HTTP endpoint is supposed to be public facing endpoint, try an alternative DNS (for
    example Cloudflare’s DNS):

    root@netdata # host -v <your_endpoint>
Verify access restrictions in the remote host

If the remote host is a Linux-based machine and you have access to it, you can check the followings.

Check the ICMP settings

In most linux distributions you can restrict the ICMP echo operations.

  1. Check your current setting.

    root@netdata # systemctl net.ipv4.icmp_echo_ignore_all

    If this value is set to 1 your system ignore incoming ICMP echo requests.

  2. To change this, bump this net.ipv4.icmp_echo_ignore_all=0 entry under /etc/sysctl.conf.

  3. Reload the sysctl settings.

    root@netdata # sysctl -p

Check your firewall rules

Depending on what firewall you use, the commands might differ from what’s shown below. For example, if you are using IP tables you can check for restriction rules upon icmp.

root@netdata # iptables -L | grep ICMP

For futher investigation or changes in your firewall settings we strongly advise you to consult
your firewall’s documentation and guidelines.