SNMP Monitoring & Architecture Simulation

What is Simple Network Management Protocol (SNMP)?

Simple Network Management Protocol (SNMP) is an Application Layer protocol running over UDP Port 161 (Polling) and UDP Port 162 (Traps/Informs). It allows Network Management Systems (NMS) to centrally monitor, query, and configure managed network devices such as routers, switches, firewalls, and servers.

SNMP Components: NMS, Agent, and MIB

• NMS (Network Management System): The central server running management software (e.g., PRTG, SolarWinds, Zabbix) that polls agents and collects traps.
• SNMP Agent: Software module embedded within managed devices (e.g., Cisco IOS) that collects local hardware/performance statistics.
• MIB (Management Information Base): A hierarchical, tree-structured database that organizes all monitorable object variables using standardized Object Identifiers (OIDs).

SNMP Protocol Versions Compared

• SNMPv1: Legacy version. Uses plain-text community strings for authentication. Lacks encryption and 64-bit counter support.
• SNMPv2c: Introduced 64-bit counters (e.g., ifHCInOctets for Gigabit interfaces) and GetBulkRequest. Still transmits community strings in unencrypted cleartext.
• SNMPv3: Current industry standard. Adds User-Based Security Model (USM) featuring **HMAC-SHA/MD5 Authentication** and **AES/DES Encryption** (Privacy).

Common SNMP Operations & PDUs

• GetRequest: Sent by NMS to retrieve specific variable values from an agent.
• GetNextRequest / GetBulkRequest: Used to traverse MIB tables efficiently.
• SetRequest: Sent by NMS to modify configuration settings on an agent device.
• GetResponse: Sent by the agent to return requested variable values to the NMS.
• SNMP Trap: Unsolicited alert sent immediately by an agent to the NMS upon critical events (e.g., Interface Down, High CPU).