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Reserve Your Seat TodaySimple Network Management Protocol (SNMP) Traps are alert messages sent from a remote SNMP-enabled device to a central collector, the "SNMP manager". In other words, SNMP Trap messages are asynchronous, unpacked messages used to notify an entity in your network management system, i.e. central management, of significant issues and events.
An SNMP Trap message might tell you that a managed device is overheating, for example. This makes SNMP Trap messages helpful for immediate alerting. Trap messages are the main form of communication between SNMP monitoring tools - an SNMP Agent and an SNMP Manager.
As you'll recall, SNMP is one possible protocol that managers and agents can use to communicate.
SNMP Trap notifications - often referred to as "incoming traps" - provide a critical tool for real-time network monitoring. These alerts instantly notify your SNMP manager of significant events occurring at the agent level. Unlike traditional polling methods where the manager periodically checks for updates, traps are pushed out as soon as an event occurs. This immediate notification capability makes SNMP Traps invaluable for proactive network management, ensuring rapid response to potential issues.
Devices like routers, RTUs, and switches often rely on SNMP Trap messages for alerting. SNMP traps are most commonly issued by one of two device types. Newer monitoring devices are able to send traps on their own to alert an SNMP trap manager when they experience a problem. For older devices that do not support SNMP, an SNMP RTU may be used to collect alarms from multiple legacy devices, convert them to SNMP traps, and transmit them (most commonly over LAN) back to your SNMP manager.
Yes. The most important thing to keep in mind is SNMP versions, like v1, v2c, and v3. Each version has different pros and cons, and you need to think about compatibility when managing your network. The type of SNMP Trap you choose will depend on your network's specific needs.
SNMPv3 supports encryption for security, while SNMPv1 is very simple to set up. If you have standardized on SNMPv3, for example, you're going to need SNMPv3 devices. Devices that send SNMP Traps in SNMPv3 maintain secure and reliable communication.
Older devices will need to be upgraded. You can also install a translation device to convert between SNMP versions. This provides compatibility for all SNMP Trap messages in your network.
There are two different methods for encoding alarm data in SNMP traps.
The first is to use what are known as "granular traps". Granular traps each have a unique OID so that you can tell them apart from one another. The SNMP manager getting the SNMP traps from the device will look up the OID in a translation file called a management information base or MIB.
Because granular traps use unique numbers to support this lookup method, no actual alarm data needs to be contained within the SNMP trap. This reduces bandwidth consumed by SNMP traps because they are not sending redundant information through the network. Efficient encoding makes sure that SNMP Trap messages do not burden your network bandwidth.
Unlike other protocols, an SNMP trap provides no proof that the message is received by the SNMP manager. This is a key limitation to address when relying on SNMP Traps. Newer versions of SNMP include a new type of message called an "inform" message. An SNMP inform message is confirmed by the SNMP manager. If SNMP agent does not see confirmation from the SNMP manager that its SNMP inform message has been received, it will resend the inform message.
Because SNMP is asynchronous (messages are sent only when something must be reported), there's also no automatic way to be sure a device is still online. This is a disadvantage compared to polled protocols, where the central master is frequently asking each device for an update.
Because SNMP is one specific protocol it's incompatible with others, like Modbus or DNP3. Despite these limitations, SNMP Trap messages remain a core tool for modern network monitoring. To address these limitations, and effectively use SNMP Traps, you need an SNMP conversion device:
It's not prominent in SNMP textbooks, but real-world network administrators know that making multiple protocols work together is part of the job. Integrating SNMP's Trap capabilities with other protocols means network teams can unify diverse monitoring tools. Here's an example of protocol conversion, as configured in an RTU web interface:
To make it easier to understand how you can monitor SNMP traps, let's look at a real-world example: the NetGuardian 832A.
This RTU sends SNMP traps based on many inputs. Typically, the 832A will send traps to your manager when one of its 32 discrete alarm inputs is triggered by a contact closure output from one of your devices. This could indicate anything from generator failure to a door open, to a motion sensor.
This 832A can also send SNMP traps based on the current status of its eight analog current or voltage inputs. Since analog inputs are never completely on or off, but rather a value in a range, the firmware and user configuration are used to decide when to send traps. The flexibility of the NetGuardian's SNMP Trap settings uphold precise alerting. Helpful software and good build quality are reasons it has been used at many telecommunications, utility, and transit companies.
The Fast Track Introduction to SNMP by Marshall DenHartog is a quick, 12-page introduction to SNMP. You'll learn about traps, message formats, the MIB, and other fundamental SNMP concepts. This resource is especially helpful for mastering SNMP Trap implementation.
Download SNMP Tutorial PDF
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That experience means that we have SNMP experts on staff. Send us a quick online message (or just give us a call) and we'll answer any SNMP question you have. Let us guide you in optimizing SNMP Trap deployment for your network.
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