Simple Network Management Protocol (SNMP)

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SNMP (Simple Network Management Protocol)

• An Internet protocol used for collecting information from managed devices on IP networks and modifying device behavior
• Managed devices include the following
  • Routers
  • Switches
  • Firewalls
  • Printers
  • Servers
  • Client devices

SNMP Manager

• A central system that collects and processes information from managed devices
• Often set up as a server, especially in large enterprise environments
• Sends and receives SNMP messages to and from agents

SNMP Agents

• Networked devices that send information about themselves to the manager
• Run background services to collect data and send it to the manager
• Transmit data at regular intervals or when requested by the manager

SNMP Message Types

• SET
  • Manager-to-agent request to change variable values
• GET
  • Manager-to-agent request to retrieve variable values
• TRAP
  • Asynchronous notifications from agents to the manager to notify significant events
  • Notify the manager of events such as uptime, configuration changes, and network downtime
  • May be granular or verbose
    • Granular
      • Sent TRAP messages get a unique object identifier OID to distinguish each message as a unique message being received
      • OID (Object Identifier)
        • Unique object identifier used to identify variables for reading or setting via SNMP
        • Allows the manager to distinguish individual SNMP trap messages
      • MIB (Management Information Base)
        • A hierarchical namespace containing OIDs and their descriptions
        • Describes the structure of device subsystem management data
        • Stores consolidated information received through SNMP traps
    • Verbose
      • SNMP traps may be configured to contain all of the information about a given alert or event as a payload
  • Data in SNMP TRAPS are stored in a simple key-value pair configuration known as a “variable binding”

SNMP Versions 1, 2, and 3

• SNMP versions 1 and 2 use plain-text community strings for access, making them less secure
• SNMP version 3 offers enhanced security features
  • Security Enhancements in SNMP Version 3
    • Integrity
      • Hashing messages before transmission to prevent data alteration
    • Authentication
      • Validating the source of messages
    • Confidentiality
      • Adding encryption using DES, 3DES, or AES
    • Dividing SNMP components into entities with different access privileges for improved security