SNMP Exporter

Prometheus SNMP Exporter

Goal

Gather metrics from SNMP enabled devices
Store metrics in the Prometheus time series database
Present metrics in Grafana dashboards

Notes

The process of collecting metrics via Prometheus is completely detached from any monitoring core. If you are new to Prometheus, first read the documentation.

Steps

Enable Prometheus & Grafana

su - SITE_USER
omd config set GRAFANA on
omd config set PROMETHEUS on
omd config set PROMETHEUS_SNMP_EXPORTER on

Get SNMP MIB files

SNMP MIB files are needed by Prometheus to translate the OIDs into human readable metric names. Most manufacturers provide their MIBs for download directly from their systems (or appliances).

Generate SNMP Exporter config

Put all needed MIB files in a location NetSNMP can read them from. Default paths are $HOME/.snmp/mibs and /usr/local/share/snmp/mibs. For OMD $OMD_ROOT/.snmp/mibs is recommended.

Add a new section to “modules” in $OMD_ROOT/etc/prometheus_snmp_exporter/generator.yml.

The example below describes a configuration for Cisco ASA Firewalls.

modules:
  CiscoASA:    # The module name. You can have as many modules as you want.
    walk:      # List of OIDs to walk. Can also be SNMP object names or specific instances.
      - sysUpTime
      - interfaces
      - ifXTable
      - 1.3.6.1.4.1.9.9.392.1
      - 1.3.6.1.4.1.9.9.147.1
    lookups:
      - old_index: ifIndex
        new_index: ifDescr
    version: 2  # SNMP version to use. Defaults to 2.
                # 1 will use GETNEXT, 2 and 3 use GETBULK.
    max_repetitions: 25  # How many objects to request with GET/GETBULK, defaults to 25.
                         # May need to be reduced for buggy devices.
    retries: 3   # How many times to retry a failed request, defaults to 3.
    timeout: 10s # Timeout for each walk, defaults to 10s.

The Prometheus SNMP exporter ships with a generator for the exporter configuration:

OMD[host]:~$ generator generate --output.path="$OMD_ROOT/etc/prometheus_snmp_exporter/snmp.yml"

Prometheus scrape config

Create a new scrape config file at $OMD_ROOT/etc/prometheus/prometheus.d/scrape_configs/static/

02-snmp-exporter.yml, for example:

  - job_name: 'snmp'
    # Override the global default
    scrape_interval: 120s
    scrape_timeout: 90s
    file_sd_configs:
      - files:
        - '/omd/sites/prod/etc/prometheus/conf.d/custom/*.json'

    metrics_path: /snmp
    params:                           # default values
      module: [if_mib]
      community: [public]
    relabel_configs:
      - source_labels: [__address__]
        target_label: __param_target
      - source_labels: [hostname]
        target_label: instance
      - target_label: __address__
        replacement: 127.0.0.1:9216    # IP:Port to reach snmp exporter
      - source_labels: [snmpCommunity] # Take community from targets
        target_label: __param_community
      - source_labels: [mib]           # Take module also from targets
        target_label: __param_module

Note

The default Prometheus SNMP Exporter requires each “module” in snmp.yml to have its own SNMP community and SNMP v3 authentication block. We have extended the exporter so that dynamic community strings are possible. We take community information from the target configuration (see the next section).

Prometheus Target config

A target defines an endpoint Prometheus has to scrape for metrics.

Put a target configuration JSON file in $OMD_ROOT/etc/prometheus/conf.d/custom/.

[
  {
    "targets": [ "192.168.1.1" ],
    "labels": {
      "hostname": "firewall.local",
      "snmpCommunity": "MySecretROCommunity",
      "mib": "CiscoASA"
    }
  }
]

You can add as many individual labels as you like. Just extend the “labels” section.

Finally

Restart both Prometheus and the Prometheus SNMP Exporter:

omd reload prometheus
omd reload snmp_exporter

Open the Prometheus web UI in your browser

https://<monitoring-host>/<omd-site>/prometheus/targets

You can see successfully scraped SNMP devices listed as targets in your web UI.

As the Prometheus data source is predefined in Grafana, you can immediately start creating dashboards with your new SNMP metrics.

Have Fun :-)