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SNMP is a networking management protocol used to monitor network-attached devices. SNMP allows messages (called protocol data units) to be sent to various parts of a network. Upon receiving these messages, SNMP-compatible devices (called agents) return data specific to certain parameters that are monitored to the SNMP manager. Furthermore to supporting SNMP services, Axigen also supports SNMP Traps.
How chart information is collected & processed
Now we will detail how the Axigen mail server collects and processes chart data and how various settings can influence the display of the charts. This will help you in the process of understanding and reading the defined charts, and further help in the process of creating new charts based on the available parameters.
When the sample interval is reached (default: once every minute), Axigen performs the following operations:
- Increases or decreases all the SNMP counters based on the read parameter information;
- Stores all the parameter information based on which charts can be created;
- The Axigen configuration file is checked for defined charts;
- After all the defined charts are inventoried. The remaining parameter data that does not correspond to a defined chart is discarded;
- If the aggregation interval is reached, the aggregation function is applied on the previously recorded values of the remaining parameters. The resulted value is written in the defined chart's database used for displaying charts;
- If the aggregation interval is not reached, then the recorded values of the parameters are stored in memory with each sample interval until the aggregation interval is reached.
SNMP configuration steps
In addition to the charts displayed in the WebAdmin interface, Axigen has a SNMP service (Simple Network Management Protocol). This service can be used as an agent that can be queried using the SNMP protocol. The SNMP agent is read-only for the Axigen configuration settings.
Additionally, the SNMP service is able to send trap signals to configured hosts in one of the following situations:
- Server start;
- Server reloading;
- Server shutdown.
This feature can be used to notify other monitoring tools about the status of the server. In their turn, these tools can be configured to notify you about the status of the server, by email, phone, pager or other means.
The SNMP Send Traps To All Managers option will determine the Axigen mail server to send trap signals to all the hosts that queried the server using the SNMP protocol when one of the previously mentioned conditions are met.
In order to find the parameters that can be monitored using the SNMP protocol, a MIB file can be downloaded by navigating to the following location:
- Login to the WebAdmin interface;
- Click on Status & Monitoring;
- Click the Reporting service link;
- Within the SNMP Parameters section, there is a link for downloading the mentioned file.
Generally, this type of file can be viewed using specialized tools that are able to interpret the format of the file and display it in a human readable form, most often as a tree. These tools are also called MIB browsers and they can be used as SNMP managers, meaning that they can query Axigen for information regarding its reporting parameters’ values. The MIB browsing tools can also be used to send and receive trap signals.
In practice, the tool for interpreting the MIB file is not necessarily required since MIB files are essentially text files that can be viewed using a text editor also.
The MIB file is used for associating a reference tag (also called OID), used to query Axigen for the value of the parameter, with the name of the parameter in a human readable way.
For example, the OID 220.127.116.11.4.1.29463.2.1 represents the reference tag for the Total mails placed in the queue parameter that returns a value which is interpreted as described below.
By querying the reporting parameters using the SNMP protocol, an odd behavior can be observed: the returned values are always increasing instead of reflecting the actual status of the reporting parameter being queried. The explanation is that the tools that retrieve information from Axigen using the SNMP protocol create charts based on the changes from the previous value of the parameter being queried, and not its actual value.
The SNMP reporting feature of the Axigen mail server was designed with the purpose of creating performance representation charts, based on the information provided by the server, in a centralized solution where multiple other services are also monitored.
A typical example is a Network Operations Center where multiple machines and devices are monitored in a centralized way and all the information is consolidated using a SNMP managing tool that interprets trap signals when critical events occur or generates charts reflecting the usage of the managed devices.