Packet loss, round trip average

SNMP status information

Bandwidth / traffic rate

Two command definitions (check_snmp and check_local_mrtgtraf) have been added to the commands.cfg file. These allows you to use the check_snmp and check_mrtgtraf plugins to monitor network routers.

A switch host template (called generic-switch) has already been created in the templates.cfg file. This allows you to add new router/switch host definitions in a simple manner.

Monitoring Packet Loss and RTA

Add the following service definition in order to monitor packet loss and round trip average between the Icinga host and the switch every 5 minutes under normal conditions.

 define service{
        use                     generic-service ; Inherit values from a template
        host_name               linksys-srw224p ; The name of the host the service is associated with
        service_description     PING            ; The service description
        check_command           check_ping!200.0,20%!600.0,60%  ; The command used to monitor the service
        check_interval          5       ; Check the service every 5 minutes under normal conditions
        retry_interval          1       ; Re-check every minute until its final/hard state is determined
        }

This service will be:

Monitoring SNMP Status Information

If your switch or router supports SNMP, you can monitor a lot of information by using the check_snmp plugin. If it doesn't, skip this section.

Add the following service definition to monitor the uptime of the switch.

 define service{
        use                     generic-service ; Inherit values from a template
        host_name               linksys-srw224p
        service_description     Uptime  
        check_command           check_snmp!-C public -o sysUpTime.0
        }

In the check_command directive of the service definition above, the "-C public" tells the plugin that the SNMP community name to be used is "public" and the "-o sysUpTime.0" indicates which OID should be checked.

If you want to ensure that a specific port/interface on the switch is in an up state, you could add a service definition like this:

 define service{
        use                     generic-service ; Inherit values from a template
        host_name               linksys-srw224p
        service_description     Port 1 Link Status
        check_command           check_snmp!-C public -o ifOperStatus.1 -r 1 -m RFC1213-MIB
        }

In the example above, the "-o ifOperStatus.1" refers to the OID for the operational status of port 1 on the switch. The "-r 1" option tells the check_snmp plugin to return an OK state if "1" is found in the SNMP result (1 indicates an "up" state on the port) and CRITICAL if it isn't found. The "-m RFC1213-MIB" is optional and tells the check_snmp plugin to only load the "RFC1213-MIB" instead of every single MIB that's installed on your system, which can help speed things up.

That's it for the SNMP monitoring example. There are a million things that can be monitored via SNMP, so it's up to you to decide what you need and want to monitor. Good luck!

	Tip
	You can usually find the OIDs that can be monitored on a switch by running the following command (replace 192.168.1.253 with the IP address of the switch): snmpwalk -v1 -c public 192.168.1.253 -m ALL .1

Monitoring Bandwidth / Traffic Rate

If you're monitoring bandwidth usage on your switches or routers using MRTG, you can have Icinga alert you when traffic rates exceed thresholds you specify. The check_mrtgtraf plugin (which is included in the Icinga plugins distribution) allows you to do this.

You'll need to let the check_mrtgtraf plugin know what log file the MRTG data is being stored in, along with thresholds, etc. In this example, we're monitoring one of the ports on a Linksys switch. The MRTG log file is stored in /var/lib/mrtg/192.168.1.253_1.log. Here's the service definition we use to monitor the bandwidth data that's stored in the log file...

 define service{
        use                     generic-service ; Inherit values from a template
        host_name               linksys-srw224p
        service_description     Port 1 Bandwidth Usage
        check_command           check_local_mrtgtraf!/var/lib/mrtg/192.168.1.253_1.log!AVG!1000000,2000000!5000000,5000000!10
        }

In the example above, the "/var/lib/mrtg/192.168.1.253_1.log" option that gets passed to the check_local_mrtgtraf command tells the plugin which MRTG log file to read from. The "AVG" option tells it that it should use average bandwidth statistics. The "1000000,2000000" options are the warning thresholds (in bytes) for incoming traffic rates. The "5000000,5000000" are critical thresholds (in bytes) for outgoing traffic rates. The "10" option causes the plugin to return a CRITICAL state if the MRTG log file is older than 10 minutes (it should be updated every 5 minutes).