By the SNMP Monitoring team · Reviewed July 2026
SNMP and Syslog sit next to each other in almost every monitoring stack, and they're often confused — but they answer fundamentally different questions. SNMP deals in structured metrics and state: typed numbers, polled on a schedule, plus traps for events. Syslog deals in events: a stream of human-readable log messages describing things that happened. One tells you the CPU is at 80%; the other tells you the OSPF adjacency just went down. They're two pillars of observability, not competitors, and this page shows exactly where each belongs and how they combine.
Parent: comparisons. Related: traps vs polling, alerting.
What SNMP provides
SNMP is a metrics and state protocol. Its main mode is polling — your manager asks a device for specific OIDs and gets back structured, typed values: an integer counter, a gauge, a timestamp, each tied to a defined OID in a MIB. On top of polling, SNMP can push traps — asynchronous notifications when something crosses a threshold or an event fires. The defining trait is structure: every value has a type and an OID, so it's immediately machine-parseable and graphable. That's what makes SNMP good at trend lines, thresholds, and dashboards.
snmpget -v2c -c public 10.0.0.20 hrProcessorLoad.1
HOST-RESOURCES-MIB::hrProcessorLoad.1 = INTEGER: 42
That 42 is a typed value you can graph over time — the essence of metric monitoring.
What Syslog provides
Syslog is an event-logging protocol (standardised in RFC 5424). Devices and applications emit a stream of text messages as things happen — a link flap, a failed login, a config change, a daemon restart — each tagged with a severity (emergency through debug) and a facility (which subsystem sent it). It typically travels over UDP or TCP port 514 to a central log server. Where SNMP gives you a number, Syslog gives you a narrative: the human-readable record of what happened, when, and how bad it was. A message looks like:
<134>1 2026-07-11T14:22:07Z edge01 bgpd - - BGP neighbor 10.0.0.1 Down (Interface flap)
That's not a metric you graph — it's an event you read, search, and correlate. Syslog's strength is forensic detail and the full story around an incident.
Comparison table
The two, side by side:
| Dimension | SNMP | Syslog |
|---|---|---|
| Data type | Structured metrics/state | Unstructured event text |
| Primary mode | Pull (poll) + traps | Push (event stream) |
| Structure | Typed OID/value | Free text + severity/facility |
| Transport | UDP 161 / 162 (traps) | UDP or TCP 514 |
| Best for | Trends, thresholds, health | Events, forensics, audit |
The clean summary: SNMP for how much / what state, Syslog for what happened.
A useful way to internalise the difference is to think about retention and shape. SNMP metrics are typically stored as time series — regularly-sampled numbers you downsample and keep for trend analysis, where the value of any single data point is low but the shape over time is everything. Syslog messages are discrete events you keep for search and audit, where any single message might be the one that explains an outage, so you retain and index them rather than average them. That's why the two feed different backends: a time-series database for the metrics, a log store or SIEM for the events. Trying to cram logs into a metrics system, or metrics into a log system, fights the shape of the data — which is another way of seeing that they're built for different jobs and belong side by side, not merged.
SNMP traps vs syslog messages
This is where the two seem to overlap, and it's worth being precise. Both SNMP traps and syslog messages are event notifications pushed from a device, so they can report the same incident — say, an interface going down. The difference is structure. An SNMP trap is a structured PDU: it carries defined OID varbinds with typed values, so a manager can parse it programmatically and act on specific fields. A syslog message is free text with a severity and facility — rich and human-readable, but not typed or schema-bound, so extracting specific values means parsing strings. Traps integrate cleanly into a metric/threshold system; syslog integrates cleanly into a search-and-correlate log system. Neither is "better"; they feed different pipelines. The trap side is covered on traps vs polling.
When to use which
Pick by the question you're answering:
- Trend graphs, capacity, thresholds? → SNMP metrics.
- Alert when a metric crosses a limit? → SNMP (poll + threshold, or a trap).
- What exactly happened, and in what order? → Syslog.
- Security audit, forensics, config-change history? → Syslog.
- Correlating "the CPU spiked and here's the log around it"? → both, together.
The rule: reach for SNMP when the answer is a number over time, Syslog when the answer is an event with context.
Using both
Mature observability uses both, because metrics and logs answer different halves of every incident. SNMP tells you that something is wrong — a link saturated, a temperature high, a device unreachable — with the numbers and thresholds that trigger the alert. Syslog tells you why — the sequence of events, error messages, and state changes around that moment. Correlating the two is where real diagnosis happens: the SNMP graph shows the spike, the syslog stream explains it. Feed metrics to your NMS and logs to a log platform (or a combined observability tool), and alert on both. How SNMP fits the alerting side is on alerting.
Frequently asked questions
Should I use SNMP or Syslog?
Both — they solve different problems. SNMP gives you structured, typed metrics and state (plus traps), ideal for trends, thresholds, and health dashboards. Syslog gives you a stream of event log messages, ideal for forensics, audit, and understanding what happened. Use SNMP for the numbers over time and Syslog for the event narrative; together they cover metrics and logs.
Are SNMP traps the same as syslog messages?
No. Both are pushed event notifications and can report the same incident, but they differ in structure. An SNMP trap is a structured PDU with typed OID varbinds a manager can parse programmatically; a syslog message is free text with a severity and facility — human-readable but not schema-bound. Traps feed metric/threshold systems; syslog feeds log search and correlation.
What port does syslog use?
Syslog typically uses port 514, over UDP (the traditional default) or TCP (for reliable delivery). SNMP, by contrast, uses UDP 161 for polling and UDP 162 for traps. They're separate ports and separate pipelines, which is part of why the two protocols coexist rather than compete in a monitoring stack.
Should I use both SNMP and Syslog?
Yes. Metrics and logs are complementary halves of observability: SNMP tells you that something is wrong with numbers and thresholds, while Syslog tells you why with the event detail around it. Correlating an SNMP metric spike with the syslog messages from the same moment is where effective diagnosis happens, so feed both into your monitoring and alert on each.
Key takeaways
- SNMP = structured, typed metrics/state (poll + traps); Syslog = event log stream.
- SNMP answers how much / what state; Syslog answers what happened.
- Syslog (RFC 5424) carries severity + facility text over UDP/TCP 514.
- Traps vs syslog: both are events, but traps are structured OID varbinds, syslog is free text.
- Use SNMP for trends/thresholds, Syslog for forensics/audit.
- They're complementary — correlate metrics and logs for real diagnosis; see alerting.