SNMP Polling for Device Reachability

SNMP polling is commonly used by network management systems to verify whether a device is reachable and responding correctly. During polling, the NMS sends an SNMP GET request to a known OID—often a simple, lightweight value such as sysUpTime or sysName. If the device returns a valid SNMP response, it confirms that:

1. The device is reachable on the network

2. The SNMP service is running

3. The device is responding within acceptable time limits

If the NMS does not receive a response after multiple retries, the device is marked as unreachable. This is often one of the earliest indicators of a problem, such as a network failure, device crash, or loss of SNMP service.

Regular polling ensures consistent monitoring by providing:

• Up/Down detection

• Response-time tracking

• Verification that SNMP functionality is operational

Because reachability checks rely on active requests rather than device-generated notifications, SNMP polling remains an essential mechanism for confirming that devices are alive and communicating, even when traps or informs are not received.

The application below outlines a basic implementation of network polling that can be used within a lab environment.

Features:

• Platform

  • Windows Desktop or Server.

• Tabs

  • Monitor: Run SNMP requests to remote devices, view live results to monitor or troubleshoot connectivity issues between the server and device.

  • Add Device: Enter SNMP parameters and save to CSV file for easy usage.

  • Devices: View/remove saved devices.

• Storage

  • Devices stored within devices.csv. When the Application starts it reads previously saved data from CSV to automatically previously used fields.

• Protocols

  • SNMPv1/v2c is strong not recommended as it offers no encryption over the network however as many legacy device do not support SNMPv3 then SNMPv1/v2c is the only option.

  • SNMP v3 (noAuthNoPriv / authNoPriv / authPriv + selectable auth/priv algorithms). It is strongly recommended to use “authPriv” as this fully encrypts the SNMP packet.

• Polling modes

  • SNMP GET request on the device’s configured OID, or PING.

• Concurrency

  • One worker thread per device each cycle for parallel checks. As the tool is intended as a light weight with minimal device count then one worker for each device speeds up the applications responsiveness.

• Run control

  • Start/Stop with LED (green = running, grey = stopped).

  • Frequency in seconds can be configured between each request.

  • Optional Duration in minutes with auto-stop at end. Ideal for running timed tests to capture response to help determine if any network issues due to dropped and captured packets.

  • Elapsed / Remaining timers (minutes and seconds).

• Results table

  • Columns: Name, IP, OK?, Message, Runs, Drops.

  • Row colour: green (success) / blue (failure).

  • Copy Table button (paste as CSV format into Excel/Sheets or docs).

• Theme

  • Light/Dark switch (Light by default).

Functions & methods.

• Add Device tab

  • Fields: Name, IP, Version (v1/v2c/v3), Community (v1/v2c), Security Level (v3), User (v3), Auth Key/Proto, Priv Key/Proto, Polling OID, Timeout (ms), Retries.

  • Dynamic visibility: v1/v2c → Community only; v3 → show security level + toggle auth/priv fields by level.

  • Buttons: Add Device (save), Import CSV (replace).

• Devices tab

  • Table with checkbox column + all device fields.

  • Remove Selected (blocked if monitoring is running).

• Monitor tab

  • Controls: Start/Stop, Mode (SNMP/PING), Frequency (s), Duration (min; 0 = indefinite), Theme, Copy Table.

  • Status: text + LED indicator.

  • Timers: Elapsed / Remaining.

  • Results: populate & colour rows; copy to clipboard.

Polling flow

• Press Start → timers reset; LED green; Poller thread starts.

• Each cycle:

  • Load devices from CSV.

  • Create a thread pool with one worker per device; run checks in parallel.

  • Update Runs/Drops; refresh table and row colours.

  • Sleep briefly; remain responsive to Stop and Duration.

• Duration > 0 → auto-stop at target time; LED grey with “Stopped (duration reached)”.

• Press Stop anytime to halt immediately.