Dynamic SNMP

Dynamic SNMP is a Pandora FMS plugin that scans an SNMP-enabled device and creates one monitoring module per network interface and metric. Instead of predefining each interface OID, it identifies interfaces by their name, so monitoring stays valid after reboots and interface changes. It can run as an agent plugin or as a server plugin that creates and maintains its own agent. By default it collects interface operational status and inbound and outbound traffic, using 64-bit counters when the device supports them.

The plugin performs an SNMP scan of a target device and builds Pandora FMS modules dynamically from the device interface table. Rather than predefining the OID of every interface, it walks the interface names, uses each interface name as the module prefix and queries the configured branches for it. The result is one module per interface and metric, named after the interface and the branch.

By default it collects the operational status of each interface and its inbound and outbound traffic. When the device exposes 64-bit counters, the plugin uses the high-capacity counters; otherwise it falls back to the 32-bit counters. For custom branches, the module data type is detected from the SNMP value returned, so additional metrics can be added without declaring their type in advance.

Scanning can be scoped and tuned: inclusion and exclusion patterns limit which interfaces are monitored, numeric and string warning and critical thresholds are attached to the generated modules and alert templates can be applied to all of them.

The plugin runs as an agent plugin, generating modules under the local agent, or as a server plugin, which creates and feeds a dedicated agent when it does not exist yet. Because modules are keyed by interface name, monitoring remains stable across device restarts and OID changes.

What it allows you to do

- Monitor every interface of an SNMP-enabled device without predefining each interface OID.
- Keep interface monitoring stable across device restarts and OID changes by keying modules on the interface name.
- Scope monitoring to specific interfaces with inclusion and exclusion name patterns.
- Apply numeric and string warning and critical thresholds to the generated modules.
- Attach alert templates to all generated modules.
- Use 64-bit network counters when the device supports them, with automatic fallback to 32-bit counters.

What it monitors

- Interface operational status
- Inbound interface traffic
- Outbound interface traffic
- Custom SNMP metric branches defined by OID subtree

How it works
The plugin walks the interface name branch of the target device and queries the configured metric branches for every interface found. Default branches cover operational status and inbound and outbound traffic; 64-bit counters are used when available, otherwise 32-bit counters. Inclusion and exclusion patterns decide which interfaces are monitored, and thresholds and alert templates are written into the generated modules. It can operate as an agent plugin or as a server plugin that creates the target agent when it does not exist.

Benefits

- Interface monitoring stays valid after device reboots and OID changes.
- Modules are created from the device interface table, avoiding the manual definition of every interface OID.
- Every interface and its metrics are covered consistently on each scanned device.
- Interface status and traffic become visible together in the same platform as the rest of the monitored infrastructure.

Use cases

- Monitoring switches, routers and firewalls with many interfaces whose OIDs change between restarts.
- Standardising interface status and traffic monitoring across a fleet of network devices.
- Limiting monitoring to interfaces that follow a specific naming convention on large devices.
- Adding custom SNMP metrics on the same per-interface naming scheme.

Requirements

- A Pandora FMS deployment with a server or an agent able to run the plugin.
- Perl 5.x.
- The net-snmp utilities snmpwalk and snmpget available in the system PATH.
- Network reachability to the target device, plus its SNMP community (v1/v2c) or its SNMPv3 user and keys.

Compatibility
Developed and tested on Rocky Linux and Fedora 34; expected to run on any Linux system. Compatible with Pandora FMS NG 784 and later versions.

Limitations

- Scanning time grows with the number of interfaces, so devices with large interface tables may need longer plugin or module timeouts.
- The module data type for custom branches is detected automatically and cannot be forced.