SNMP for monitoring industrial networks
SNMP basics for automation networks: agents, MIBs and OIDs, polling vs traps, v1/v2c vs v3 security, what to monitor on switches and how to integrate with SCADA.
SNMP (Simple Network Management Protocol) lets a monitoring system read status from switches, routers, UPS and other devices and receive event notifications. Managed industrial switches all support it, and many SCADA packages have SNMP drivers.
Building blocks
| Term | Meaning |
|---|---|
| Agent | SNMP service on the device (UDP 161) |
| Manager | Monitoring system or SCADA driver that polls agents |
| MIB | Description of available objects; standard (IF-MIB, BRIDGE-MIB) and vendor MIBs |
| OID | Numeric object identifier, e.g. 1.3.6.1.2.1.2.2.1.8 = ifOperStatus |
| Trap / inform | Event sent by the agent to the manager (UDP 162), e.g. link down, ring open |
Versions
- v1/v2c: community strings ("public"/"private") sent in clear text — read-only at most, and never with default communities.
- v3: users with authentication (SHA) and encryption (AES); use it wherever the manager supports it.
What to monitor on switches
- Port link status and speed/duplex (unexpected 10 Mbit/half duplex = cabling problem).
- Interface error counters (CRC/alignment errors, discards) — rising counters show bad cables or EMC problems.
- Ring/redundancy status (MRP, vendor rings), power supply and temperature alarms.
- Port traffic (multicast storms, broadcast load).
Practical tips
- Poll every 30–60 s; use traps for fast events.
- Keep SNMP on a management VLAN; restrict which managers may query.
- Map key states into SCADA alarms so operators see "network ring open" before the second fault stops production.
Connections
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Sources
Updated 2026-10-04