Random ping loss after Debian upgrade

[Blažej Krajňák]

Hi there,

I use Zabbix 4.0 LTS which uses fping to perform ICMP checks. After Debian upgrade from 10 to 11 (including fping from 4.2 to 5.0) I experience random "fake" ping loss. It happens few times a month, so it's really hard to investigate.

Fping always runs with parameters:

fping -C10 -i0 -S 109.236.X.X < /tmp/zabbix_server_X.pinger

In the attachment is graph from todays incident. I can not determine if problem is related with vmware hypervisor, Debian, Zabbix itself or fping. I tried to change mq qdisc to fq with no change. Debians and hypervisors packet drop counters look to be clean.

Anyone has an idea?

Thanks

Blažej