Notification when SNMP host unreachable?

[herta]

When Zabbix cannot contact a Zabbix Agent, it will mark the event in the System status on the Dashboard, and it can send a notification.

Can the same be done for systems being monitored through SNMP?

We have a number of systems behind a firewall that blocks ICMP, and SNMP-monitoring is our only option. We are looking for a way to detect when such a system fails.

[Colttt]

i think you can use nodata

[herta]

i think you can use nodata

Thanks, but we tried that. It looks like zabbix does not evaluate items when it cannot reach the host.

It's frustrating. The fact that the SNMP icon turns red indicates that the info about the host being unreachable is available somewhere. I just cannot find where that might be.

[Heilig]

Additionally, you can check the availability of port 161 (up/down) and regarding its accessibility judge about availability of the host.
Update: or from a database by query get the host status.

[herta]

Hello Heilig,

Additionally, you can check the availability of port 161 (up/down) and regarding its accessibility judge about availability of the host.

How would you accomplish that? when zabbix cannot contact a host, it cannot get new values for its items and therefore will not launch the trigger.

Update: or from a database by query get the host status.

So, basically, run an external script on the zabbix server that checks whether new data have been entered for those hosts in the zabbix database? Or alternatively, run an external script on the zabbix server that tries to get a single snmp value from those hosts?

[Heilig]

How would you accomplish that? when zabbix cannot contact a host, it cannot get new values for its items and therefore will not launch the trigger.

Zabbix can connect to a host on SNMP port (161), am I right? If so, you can use simple or telnet checks for getting port status (zabbix agent is not needed for this checks).

So, basically, run an external script on the zabbix server that checks whether new data have been entered for those hosts in the zabbix database? Or alternatively, run an external script on the zabbix server that tries to get a single snmp value from those hosts?

No. You can use ODBC or some script to get snmp agent state for necessary host from zabbix DB.
Look at "hosts" table in Zabbix DB, column name "snmp_available", if value 1 - snmp agent is Ok on server and has green "snmp icon" in zabbix frontend.

[herta]

Zabbix can connect to a host on SNMP port (161), am I right? If so, you can use simple or telnet checks for getting port status (zabbix agent is not needed for this checks).

A Simple check with net.tcp.service[telnet,,] indeed seems to do the trick.

Thanks, Heilig.