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What is The Purpose of The SNMP Trap Message?

SNMP is a common communication protocol used in network management systems to allow devices to exchange information. SNMP has a wide acceptance in the remote monitoring industry due to its ability to support many different network devices, from many different manufacturers - allowing them to work together.

If you are network operator, you most probably need to work with the SNMP protocol and consequently with its messages. SNMP comprehends many different types of messages, and we'll dive into SNMP trap messages to learn more about it.


SNMP and SNMP Structure

Simple Network Management Protocol (SNMP) is used in network monitoring to watch equipment located at several different remote sites. SNMP remote monitoring systems help companies and organizations to save time and money, because they don't need to send out techs to far away locations to keep an eye on mission-critical equipment and to solve issues.

SNMP is based on the manager-agent model.

SNMP structure
SNMP uses a manager/agent architecture model. Traps alarm messages are sent by the SNMP agent to the manager.

In this model, the SNMP agent are remote network equipment. These gear will vary according to each network, but some examples are: servers, routers, switches, or any other SNMP-enabled device. An SNMP manager sends requests and, in return, gets the agent's responses. SNMP managers can be any device that has the purpose to collect and process information, while also providing an interface for human operators.

This information exchange is done through basically five different message types:

  1. Traps

  2. Get

  3. Get-Next

  4. Get-Response

  5. Set

Each and every one of these messages have a specific purpose that make SNMP communication possible between agents and manager.


What Are SNMP Traps?

In a usual network management system, the SNMP manager polls agents prompting them to send status information to the master.

An SNMP trap message is an unsolicited message sent from an agent to the the manager. The objective of this message is to allow the remote devices to alert the manager in case an important event happens.

In other words, traps don't need a status request from the master. They are only generated and sent when an agent needs to report to the manager that something wrong is going on. For example, a trap might alert that a machine is overheating.

The trap is the only SNMP message initiated by the agent. All the other types of messages are created by the manager or are a response from a manager request. This uniqueness of trap message makes it vital to most remote monitoring systems.


Benefits of SNMP Traps

Implementing SNMP into your network can bring you many advantages.

With SNMP traps, network operators don't need to request the status of each and every individual device within the network. Instead, managed devices will simply send unrequested alerts in the form of an autonomous message - the trap.

This brings us to another benefit of using traps: they trigger instantly. You won't have to wait for a status request from the manager.

In all, traps are a great way to stay on top of the performance of your remote equipment.


Types of Trap Messages

There are two main different methods to translate significant events into trap messages.

Granular Traps

When a trap message is assembled in the granular format, each trap is given a unique identifier. This identifier allows the manager to distinguish each trap. The meaning of each identifier is stored in a translation file called Management Information Base (MIB).

Variable Bindings

When an SNMP manager assembles traps in the variable bindings format, each trap is assigned the same ID number and alarm data is stored in the variable bindings of the trap. What differentiates each message is the information contained in each trap. This could be that a door is open or a battery level is low.


Common Trap problems and How to Avoid Them

Often times, SNMP issues are caused by the traps being sent out. So, if you are experiencing SNMP problems, you might want to troubleshoot your trap messages.

Different SNMP Versions

The SNMP protocol has three major versions:

  1. SNMPv1

    This version was released in 1988, and it is the oldest and easiest to setup version of SNMP. On the other hand, the biggest disadvantages of this version are the lack of security and it only supports 32-bit counters.

  2. SNMPv2c

    The version v2c is basically identical of v1, the only main difference is the added support to 64-bit counters.

  3. SNMPv3

    Although being more difficult to setup, the version 3 was released to deal with security issues. It brings encryption for the packets and authentication as its main security features.

If your SNMP manager is configured to only accept v1 traps, but your equipment is sending v2 traps, there will be compatibility problems. Also, at the same time, if you have your manager configured to to work with v2 traps, it will not properly parse v1 traps.

So, to solve this issue, you need to configure your RTU to send traps in the SNMP version that your manager is able to accept, or setup your manager to work with the type of trap your remote equipment is sending out.

Another way to handle this issue is to invest in an advanced SNMP manager that was designed to handle any kind of SNMP version.

Non-Standard Traps

Another important point to keep in mind when working with trap messages is to check if a device is sending non-standard traps.

Even though SNMP is a standard protocol, some manufacturers have modified trap formats to meet their special requirements. So, before buying any SNMP-enabled device, make sure it will be able to smoothly integrate with your current network.


SNMP Trap Application: County Police/Fire Radio Agency

I just visited a client at a county police/fire/safety radio agency. He gets 3800 alarms per day, so that's a lot of SNMP traps coming in. There are other types of SNMP messages, like SETs, but this client doesn't use those much. His system mostly just manages SNMP traps.

For this project, he's looking to install a top-level manager to collect SNMP traps generated by his Harris RNM system. The new top-level manager, a T/Mon MINI from DPS Telecom, will process the thousands of daily SNMP traps and poll about 16 NetGuardian RTUs to keep track of all 16 radio facilities throughout the county.

The county has multiple networks set up for security compartmentalization. All networks are used for SNMP communication. They're merely separated so that a single intrusion only gains access to one network.

This security provision is to satisfy federal requirements enforced by regular FBI audits. The 6 NICs on the T/Mon master suit this requirement well. T/Mon can collect alarms from each independent network without routing traffic between them.

We also discussed alternatives to the SNMP trap message type in the future. This client would love a T/Mon smartphone application. Using this, several technicians could effectively be carrying the monitoring system in their pockets.

When a new alarm comes in, alerts would be sent simultaneously. The first person to acknowledge the alarm would get it added to their personal list, and the others would be notified to spend time on other work.

This is just one possibility for a future that will involve SNMP and trap messages at the core, but that increasingly leverages modern technology to make the collected data contained in traps easier to understand and control.


The Bottom Line

SNMP traps are basic alarm messages. If used correctly they are are able to give you company many important benefits. But, it all comes down to having a proper SNMP deployment with perfect-fit monitoring devices.

Our team of experts can help you in your SNMP management endeavors. Contact us today and get a system that will meet your needs 100%.

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