---
type: Monitoring Guide
title: "How to Monitor Interface Errors & Discards via SNMP"
description: "Read ifInErrors/ifOutErrors and discard counters, compute an error rate against packets, and triage physical vs congestion causes."
resource: "https://snmp-monitoring.info/monitoring/network/interface-errors/"
tags: [monitoring]
timestamp: 2026-07-11T00:00:00Z
---

# How to Monitor Interface Errors & Discards via SNMP

Read ifInErrors/ifOutErrors and discard counters, compute an error rate against packets, and triage physical vs congestion causes.

## Related concepts

- Up: [SNMP Network Monitoring: Interfaces, Bandwidth & Errors](/monitoring/network/index.md)

## Frequently asked questions

### What OID shows interface errors in SNMP?

Inbound errors are ifInErrors (1.3.6.1.2.1.2.2.1.14) and outbound are ifOutErrors (1.3.6.1.2.1.2.2.1.20). For dropped-but-valid packets use ifInDiscards (.13) and ifOutDiscards (.19). All are cumulative Counter32 objects.

### What's the difference between errors and discards?

Errors are malformed packets — failed CRC, bad framing — which point at a physical problem like a cable, connector or duplex mismatch. Discards are valid packets dropped because a buffer or queue was full, which points at congestion or undersized queues. Different counters, different fixes.

### What causes interface errors?

Most commonly a duplex mismatch, a bad or overlong cable, a dirty fiber connector, or a failing transceiver. EMI and grounding issues are rarer. Because these are physical-layer faults, you chase them with cable swaps and optics checks, not config tweaks — unless it's a duplex mismatch, which is a config fix on both ends.

### Should I alert on total errors or the error rate?

The rate. Lifetime totals only grow and say nothing about now — a year-old switch will show thousands of harmless historical errors. Alert on the change per interval, ideally as a ratio of errors to packets, so a busy link and an idle one are judged fairly.

## Source

Concept generated from https://snmp-monitoring.info/monitoring/network/interface-errors/ — the SNMP Monitoring vendor-neutral knowledge base. Content is limited to what that page states (no external claims added here).