Debian 9

Hi,
You said that
If it works well for internal network, but not for external clients
These are passive agent checks that are failing from zabbix server to zabbix agent.
Please check those two things first:

• Zabbix server tries to connect to remote agent port 10050. Is this port open on firewall ? you can test it with command

   telnet remote_ip_address 10050

  , where remote_ip_address is IP address of zabbix agent.

• if the communication ports are open, the connection to zabbix agent may just simply time out because of poor network performance. The default timeout in zabbix is 3 seconds in zabbix_server.conf

  ### Option: Timeout
  #       Spend no more than Timeout seconds on processing
  #
  # Mandatory: no
  # Range: 1-30
  # Default:
  # Timeout=3
  

You can increase this value in zabbix_server.conf file, Zabbix Server restart is needed after configuration changes.

Thank you for your answer, when you say telnet it means to make a telnet from the zabbix server to the remote agent so the remote machine, our old Zabbix version 2.2 we opened the firewall from the agent on the machines to our server Zabbix, we also changed the timeout to = 30 and it still does not work, we have a new message "Get value from agent failed: ZBX_TCP_READ() failed: [104] Connection reset by peer", thank you for your support

Hello,
All tests of Telnet pass, here is also the Zabbix agent log and some screenshots and configuration files of the Zabbix server, thank you for your help

Hello,
There is a line in yor zabbix_agentd.conf

Server=127.0.0.1

On all your agents to make passive checks work, this IP must match Zabbix Server ip address

You can test the answer from zabbix agent in the following way:
Execute from the command_line the following command on the Zabbix server

zabbix_get -s AGENT_IP_ADDRESS -k agent.ping

where AGENT_IP_ADDRESS is IP address or DNS name of any of your non-responsive hosts.
You will see in answer the correct value, or error message explaining why you can't get a value

If you do not have zabbix_get utility installed on Zabbix server, you can get it for debian 9 with

apt-get install zabbix-get

you can read more about it here
https://www.zabbix.com/documentation/3.4/manual/concepts/get

This issue tracker is for bug reports only. No indication of a bug in this particular report. Please use IRC, forums or other channels for community support - see https://www.zabbix.org/wiki/Getting_help for more details.Alternatively contact [email protected] for commercial support.Closing as Commercial support required.

Inicie o serviço do agente:

#service zabbix-agent start