zabbix agent is intermittent down for a few minutes

[robertchen]

please help, when I got to the agent log, I see nothing.

I can do both ways telnet zbx server 10051, zbx agent 10050.
But I got alerts like: Zabbix agent on *MYHOST* is unreachable for 5 minutes

please see the pic attached:

[filipp.sudanov]

I would probably suggest to check the following:
- Any Antivirus/Firewall software runing on agent - zabbix opens and closes TCP connections all the time and sometimes firewalls don't like it
- May be too high CPU load on the monitored machine
- Isn't it a network problem, any routers that may get restated on they own?

You can add a simple check with icmpping of that machine. This check will not be dependent on zabbix agent. Afterwards you'll be able to compare the graphs - if agent ping and icmpping will be missing together, or not.