Link state polling
Link state polling monitors changes to the status of the following interface MIB variables: ifOperStatus and ifAdminStatus.
If the value of one of these MIB variables changes between poll intervals, an event is raised.
The
initial state of link state polls is determined by any existing link state events on the
interface. If there are no existing link state events, then the initial state is set to Clear. If
many interfaces in your network do not have their administrative status set, you might want to
determine the initial interface state by polling the interface instead. To set the initial state
of the interface using a poll, set the UseFirstPollForInitialState configuration
option in the NcPollerSchema.cfg configuration file.
When storing SNMP Link State data in the NCPOLLDATA polling database the data is not stored every poll cycle. The data is stored either upon the detection of a state change, or after 15 minutes, whichever happens first. If a state change occurs then the previous and current values are stored. If there is no state change then the current value is stored.
- 3: available
- 2: administrative interface is down
- 1: unavailable
Example
If the value of ifOperStatus was 1 (up) during the previous poll, and changes to 2 (down) in the current poll, an event is raised.The following table shows the events that are generated as a result of the changes in interface status. Additionally, an event is generated when a poll fails to return any data, and an event with a clear severity is generated when a poll to the same device subsequently succeeds.
| Status of the ifAdminStatus MIB variable between poll intervals | Status of the ifOperStatus MIB variable between poll intervals | Event generated | Event Severity |
|---|---|---|---|
| Remains 1 (up) | Changes from 1 (up) to 2 (down) | The interface has gone down. | Minor |
| Remains 1 (up) | Changes from 2 (down) to 1 (up) | The interface has come up. | Clear |
| Changes from 1 (up) to 2 (down) | Changes from 2 (down) to 1 (up) | The interface has come up, although it should be down. | Clear |
| Changes from 1 (up) to 2 (down) | Remains 2 (down) | An administrator has confirmed that the interface should be down. | Clear |
| Changes from 2 (down) to 1 (up) | Changes from 1 (up) to 2 (down) | The interface has gone down. | Minor |
| Changes from 2 (down) to 1 (up) | Remains 2 (down) | An administrator has instructed the interface to come up, but it hasn’t. | Minor |