foreplay:

I created two Linux systems (rhel7 and cent7) in the VM virtual machine, one as the ZABBIX server and the other as the ZABBIX client. However, when using the server to monitor the client, the icon is red and cannot be monitored. The error message is: get value from agent failed: cannot connect to [[Client’s IP]: 10050]: [113] no route to host
The alarm roughly means that the host cannot be monitored

Linux version: CentOS 7

ZABBIX version: ZABBIX 3

Solution:

(1) Using the ping command

Server Ping client address

If Ping is enabled, the network is OK

(2) Reasons for firewall

CentOS 7 has two firewalls, a firewall and iptables. Firewall is used as the firewall by default

#service firewall status   //View firewall status

#systemctl firewall stop   //Turn off the firewall

#service firewall start   //Turn on firewall

#service firewall restart   //Reopen the firewall

the command of iptables protective wall is similar to that of firewall. Just change the name

after the firewall is closed, restart the ZABBIX client

#systemctl restart zabbix-agent   //Restart ZABBIX client