Configure SNMP monitoring

What it is

SNMP polling feeds the Bandwidth charts in Network Observatory: inbound and outbound traffic per interface, in Mbps. CreaRack reads the standard interface counters (64-bit ifHCInOctets/ifHCOutOctets, with automatic fallback to the 32-bit ifInOctets/ifOutOctets when a device does not update the high-capacity counters).

Two SNMP versions are supported: v2c (a read-only community string) and v3 (USM) (user, authentication and privacy keys).

Where the credentials live

SNMP credentials reach a monitoring target in three ways. In all of them, secrets are encrypted at rest and the API only ever returns has_* flags — your browser never receives a stored community or key back.

1. Inherited from the device profile. If the device was discovered with the Auto-Provision wizard, or you typed its credentials in the device Config modal, they live in the device profile. When you enable monitoring for that device (or send it to Observatory), the server copies them to the target on its own — and if a target is linked to a profile later on, or was created by hand without credentials, the profile’s credentials are still the ones the Local Agent polls with. You do not re-enter anything.
2. The device Config modal. Open the device’s Config modal from the monitoring pages to edit the profile credentials. Pick the version (v2c or v3 (USM)) and fill in what you want to change.
3. The per-target SNMP Settings modal. Inside a device tab in Observatory, the SNMP Settings modal sets the operational details: Community String, Port (default 161) and the Interface to monitor. Saving auto-enables SNMP monitoring for the target. The port you set here is also the one the Local Agent (2.24.0 or later) uses for deep discovery and OID probes of that device.

A target created with Add target (name + IP) starts with ping only: SNMP is switched on afterwards from its SNMP Settings, with its community string, so a target never polls with a placeholder community in silence.

How to edit credentials in the Config modal

The Config modal never shows a stored secret. Fields for secrets start empty:

• v2c: the Community field is a password input. If a community is already saved you see the hint “A community is stored. Leave blank to keep it unchanged.” Type a new value only when you want to replace it — an empty field keeps the stored one.
• v3 (USM): fill Username, Auth protocol (SHA or MD5), Auth key, Priv protocol (AES or DES) and Priv key. If keys are already saved you see “Keys are stored. Leave blank to keep them unchanged.”
• Click Save. Only the fields you typed are sent.

In device info cards the community appears masked as •••••• — that means a credential is stored, not that the value is “dots”.

How to pick the interface

1. In the device tab, open SNMP Settings.
2. The Interface dropdown lists the interfaces found on the device, with name, index and link speed (interfaces that are down are flagged (DOWN)).
3. Pick the interface whose traffic you want on the Bandwidth chart and Save.

If you never pick one, CreaRack chooses for you: the fastest physical interface that is up among the ones discovered on the device (virtual links such as bridges, bonds or WDS are skipped). Pick one yourself when the device has several active uplinks and you want a specific one as the primary.

You do not need to change the primary to look at another interface: the Agent (2.22.0 or later) polls every interface selected in the device’s card (up to eight) and keeps one series per interface, so the interface selector on the Bandwidth chart switches the chart instantly between them. The primary is marked (primary) in that selector.

Polling and reachability

• The device is polled — and its charts refresh — at its Polling cadence: 15 s, 30 s, 1 min (default) or 5 min, set in the card editor. See [[crearack—network—device-page]]. Faster cadences increase SNMP load on the device.
• The CreaRack cloud only probes public IP addresses. Devices on private LAN ranges are polled by the Local Agent in Sentinel mode, which also keeps polling 24/7 when no tab is open.

When there is no bandwidth data

With the Local Agent 2.24.0 or later, the Bandwidth section of a device tab tells you why there is no data instead of staying silently empty. A line such as “No bandwidth data: the device has no octet counters on interface 1 (wrong ifIndex?)” appears under the section header, with the time since the problem started. The possible reasons:

• the device does not answer SNMP — wrong community/keys, SNMP disabled, or a firewall in between.
• the device has no octet counters on interface N (wrong ifIndex?) — pick another interface in SNMP Settings.
• the interface counters are all zero (interface down?) — the interface exists but carries no traffic.
• the counters wrapped; a new baseline is being taken — transient; data resumes on the next poll.
• the last sample was discarded as an impossible spike (> 10 Gbps) — transient, usually after a device reboot.
• the SNMP request hangs — the device accepts the packet but never replies within the time limit.

The line disappears on its own as soon as the Agent gets a valid measurement again. It comes from the Agent’s heartbeat, so it can lag up to about 30 seconds behind the device.

Troubleshooting

Related

• [[crearack—monitoring—que-es-observatory]] — module overview
• [[crearack—monitoring—metricas]] — metrics collected and retention
• [[crearack—monitoring—ping-http]] — ICMP and HTTP monitors
• [[crearack—monitoring—alertas]] — bandwidth thresholds and alerts
• [[crearack—network—auto-provision-wizard]] — discovery that seeds the credentials
• [[crearack—settings—credential-store]] — how CreaRack stores secrets
• [[crearack—network—device-page]] — the card editor and the polling cadence

Véase también

• [[crearack—monitoring—que-es-observatory]]
• [[crearack—monitoring—metricas]]
• [[crearack—monitoring—ping-http]]
• [[crearack—monitoring—alertas]]
• [[crearack—network—auto-provision-wizard]]
• [[crearack—settings—credential-store]]