Hello James Kiarie,
Thank you for your reply. Firewall is not running (disabled) for all nodes. SELinux is disabled.

Please find below Node01 settings if it can help
[root@node01 ~]# sestatus
SELinux status: disabled
[root@node01 ~]#
[root@node01 ~]#
[root@node01 ~]# firewall-cmd –list-ports
FirewallD is not running

[root@node01 ~]# systemctl status firewalld
● firewalld.service – firewalld – dynamic firewall daemon
Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
Active: inactive (dead)
Docs: man:firewalld(1)
[root@node01 ~]#

[root@node01 ~]#
[root@node01 ~]#
[root@node01 ~]# grep -vE ‘#|^$’ /etc/zabbix/zabbix_agentd.conf
PidFile=/run/zabbix/zabbix_agentd.pid
LogFile=/var/log/zabbix/zabbix_agentd.log
LogFileSize=0
Server=192.168.1.20 #### Zabbix Server IP
ServerActive=192.168.1.20
Hostname=192.168.1.40 #### Node01 IP
Include=/etc/zabbix/zabbix_agentd.d/*.conf
[root@node01 ~]#
[root@node01 ~]#
[root@node01 ~]# systemctl status zabbix-agent
● zabbix-agent.service – Zabbix Agent
Loaded: loaded (/usr/lib/systemd/system/zabbix-agent.service; enabled; vendor preset: disabled)
Active: active (running) since Mon 2022-09-26 15:38:46 EAT; 3 days ago
Process: 11373 ExecStop=/bin/kill -SIGTERM $MAINPID (code=exited, status=0/SUCCESS)
Process: 11376 ExecStart=/usr/sbin/zabbix_agentd -c $CONFFILE (code=exited, status=0/SUCCESS)
Main PID: 11379 (zabbix_agentd)
Tasks: 6
CGroup: /system.slice/zabbix-agent.service
├─11379 /usr/sbin/zabbix_agentd -c /etc/zabbix/zabbix_agentd.conf
├─11380 /usr/sbin/zabbix_agentd: collector [idle 1 sec]
├─11381 /usr/sbin/zabbix_agentd: listener #1 [waiting for connection]
├─11382 /usr/sbin/zabbix_agentd: listener #2 [waiting for connection]
├─11383 /usr/sbin/zabbix_agentd: listener #3 [waiting for connection]
└─11384 /usr/sbin/zabbix_agentd: active checks #1 [idle 1 sec]

Sep 26 15:38:46 node01 systemd[1]: Stopped Zabbix Agent.
Sep 26 15:38:46 node01 systemd[1]: Starting Zabbix Agent…
Sep 26 15:38:46 node01 systemd[1]: Started Zabbix Agent.

Hello Magwai. Kindly ensure that port 10050 has been opened on the firewall for all the nodes in your setup. Then restart the firewall for the changes to come into effect. Let me know how this goes.

Thank you for this good explanantion, I have added hosts on Zabbix 6 however all Linux host are grayed out, inteface status is showing unknown. What can I do to make them available (green color?)