Dears,

specification are:

OS:centos 7.0

DB:mariaDB(Galera)

zabbix version 4.0.4

I restarted my zabbix server. After couple of  time zabbix generated false notification with such a this description: "zabbix agent on 'server' is unreachable for 5 minutes also start time is greater than end time"  in most of host names which I had defined. issue has been token place for 3 days although previous notifications are working in the correct format.

before restarting I did below actions I don't think that they are very important.

1-  executing "nmap n -PN -sT -sU -p localhost" for finding all listening ports.

2- changing  Database hostname and back it to normal one in less than zero one minute time.

after occurring issue, these are works which I've done:

1- checking timezone in all configs (php.ini, zabbix.config,..) which I know and set them to current time zone.

2- checking logs in Proxy ,Zabbix server, but I didn't find any useful information.

3- check all setting which I implemeted in zabbix installation time however all things were normal.

Could you please support?