How to monitor the operational status of a router link using SNMP?

The operational status of a router link can be monitored by using a "Threshold" shooter. The status can be determined by reading the value of the "ifOperStatus" field (MIB-2 ifEntry sub-tree) of the router's interface used for the link. The status of an interface is "up" if an ifOperStatus.X SNMP Get request returns value 1 (X is the instance of the interface).

Before you start building the shooter determine the instance of the router's interface and the polling interval to use. You can - for example - use a 10 second polling interval for important links and 100 sec. for less important ones.

The description below assumes that your router is up-and-running and reachable through SNMP!

Building the threshold Shooter takes the following steps:

1. Switch to Designer mode
2. Right-click the router on the map from which you want to monitor the link status and select Define Shooters (Manually)
3. Right-click somewhere in the Shooters box and select Add a Shooter
4. Give the new Shooter a name, select Threshold 10 from the Shooter-type box and click Save
5. In the MIB tree browse to "iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable.ifEntry"
6. Right-click the "ifAdminStatus" leaf and select Inspect. The leaf should now have turned green! If not so, the router didn't respond to your SNMP request. Verify the IP address and Community name in the Test and Inspect box at the right of the window!
7. Right-click the (green) leaf again and select Add to the selected Shooter. A new sub-window opens that lets you customize the Shooter-target: ifAdminStatus!
8. In the OID/Instance box check the Append radiobutton and enter the interface's instance (preceded by a dot)
9. In the Threshold settings box select the "<>" operator, enter "1" in the value edit box and check the Raw radiobutton.
10. Click the Add/Modify button to save your settings
11. Close the "Define .. Shooters" window"
12. Finally, we have to start the new Shooter for the router to monitor. Right-click the router icon on your map and select Shooter/Properties.
13. Click the Background Shooters tab
14. Right-click your Shooter in the Available box and choose Start this Shooter for device...
15. Ready!