Snmp_monitoring

Chapter 40: SNMP and Network Monitoring

Overview

This chapter covers SNMP (Simple Network Management Protocol) for network monitoring.

40.1 SNMP Basics

SNMP Versions

              SNMP Versions
+------------------------------------------------------------------+
|                                                                   |
|   SNMPv1   - Original, security by community string              |
|   +------------------------------------------------------------+ |
|   | Read-only and read-write communities                       | |
|   +------------------------------------------------------------+ |
|                                                                   |
|   SNMPv2c  - Like v1 with enhanced operations                   |
|   +------------------------------------------------------------+ |
|   | GetBulk, GetNext improvements                              | |
|   +------------------------------------------------------------+ |
|                                                                   |
|   SNMPv3   - Secure version                                     |
|   +------------------------------------------------------------+ |
|   | User-based (USM), View-based (VACM)                        | |
|   | Authentication: MD5, SHA                                  | |
|   | Encryption: DES, AES                                      | |
|   +------------------------------------------------------------+ |
|                                                                   |
+------------------------------------------------------------------+

40.2 SNMP OIDs

Common OIDs

# System
1.3.6.1.2.1.1.1.0   - sysDescr
1.3.6.1.2.1.1.3.0   - sysUpTime
1.3.6.1.2.1.1.5.0   - sysName

# Interface
1.3.6.1.2.2.1.1.2   - ifNumber
1.3.6.1.2.2.1.2.2   - ifDescr
1.3.6.1.2.2.1.10.2  - ifInOctets
1.3.6.1.2.2.1.16.2  - ifOutOctets

# CPU
1.3.6.1.4.1.2021.10.1.5.1 - laLoad.1 (5-min)
1.3.6.1.4.1.2021.10.1.6.1 - laLoad.2 (10-min)

# Memory
1.3.6.1.4.1.2021.4.5.0   - memTotalReal
1.3.6.1.4.1.2021.4.6.0   - memAvailReal
1.3.6.1.4.1.2021.4.11.0  - memTotalFree

40.3 SNMP Tools

snmpwalk

# Walk all OIDs
snmpwalk -v2c -c public localhost

# Walk system OIDs
snmpwalk -v2c -c public localhost system

# Walk interface info
snmpwalk -v2c -c public localhost interfaces

# Get specific OID
snmpget -v2c -c public localhost sysUpTime.0

# Get multiple OIDs
snmpget -v2c -c public localhost sysUpTime.0 sysContact.0

snmpget

# Get system description
snmpget -v2c -c public localhost sysDescr.0

# Get interface statistics
snmpget -v2c -c public localhost ifInOctets.1 ifOutOctets.1

# Get CPU load
snmpget -v2c -c public localhost laLoad.1

40.4 SNMP Configuration

snmpd Configuration

# /etc/snmp/snmpd.conf (snmpd.conf)

# SNMPv2c community
rocommunity public
rwcommunity private

# SNMPv3 user
createUser admin MD5 "mypassword" DES
rouser admin authPriv

# System location
syslocation "Data Center Rack 1"
syscontact admin@example.com

# Agent configuration
agentAddress udp:161

Client Configuration

# Default community
defCommunity public

# Default version
defVersion 2c

40.5 Network Monitoring Tools

nagios-plugins

# Check CPU
check_cpu -w 80 -c 90

# Check memory
check_memory -w 80 -c 90

# Check disk
check_disk -w 20% -c 10% -p /

# Check load
check_load -w 1.5,1.2,1.0 -c 2.0,1.8,1.5

Monitoring Tools Comparison

# Nagios/Icinga      - Traditional monitoring
# Zabbix             - Enterprise monitoring
# Prometheus         - Metrics-based
# Grafana            - Visualization
# Cacti              - Graphing (RRDTool)
# Smokeping          - Latency monitoring

Summary

In this chapter, you learned:

✅ SNMP versions and security
✅ Common OIDs
✅ SNMP tools (snmpwalk, snmpget)
✅ SNMP configuration
✅ Network monitoring tools

Part 8 Summary

In this part, you learned:

✅ System logging (rsyslog, syslog-ng)
✅ Logrotate for log management
✅ System monitoring tools
✅ Prometheus and Grafana
✅ SNMP monitoring

Next Chapter

Chapter 41: Backup Strategies and Concepts

Last Updated: February 2026