📘 CCNA 200-301 v1.1

4.4 Explain the function of SNMP in network operations

1. What is SNMP?

• SNMP stands for Simple Network Management Protocol.
• It is a protocol used to monitor, manage, and control devices on a network.
• Devices can include routers, switches, servers, printers, and other network devices.
• Think of SNMP as a language that network devices use to report their health and status to network administrators.

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2. Key Components of SNMP

SNMP works using three main components:

1. Managed Devices
   • These are devices like routers, switches, or servers that SNMP can monitor.
   • Each device stores information about itself in a Management Information Base (MIB).
   • Example: A router can store its CPU usage, memory usage, and interface status in its MIB.
2. SNMP Agent
   • This is software running on the managed device.
   • The agent collects data from the device and sends it to the network management system (NMS) when requested.
   • It can also act on commands from the NMS, like resetting an interface.
3. Network Management System (NMS)
   • This is software running on a server or workstation that monitors and controls multiple devices.
   • Example tools: SolarWinds, PRTG, or open-source tools like Zabbix.
   • The NMS can read device data, generate alerts, and send commands back to devices.

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3. How SNMP Works

SNMP uses three main types of messages (called protocol data units – PDUs):

1. GET – The NMS asks the agent for specific information.
   • Example: “What is the CPU usage of this router?”
2. SET – The NMS tells the agent to change a setting on the device.
   • Example: “Turn off this interface” or “Change this device’s hostname.”
3. TRAP – The agent sends an unsolicited alert to the NMS when something important happens.
   • Example: “My interface went down” or “CPU usage is over 90%.”

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4. Versions of SNMP

There are three main SNMP versions you should know for CCNA:

Version	Security Level	Notes
SNMPv1	Community string (plain text)	Very basic, not secure.
SNMPv2c	Community string (plain text)	Improved performance, still not very secure.
SNMPv3	Username/password, encryption	Secure. Recommended for real networks.

• Community string is like a password, used in SNMPv1 and v2c.
• v3 adds authentication and encryption, so data cannot be easily read or changed by attackers.

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5. SNMP Data Structure – MIB and OID

1. MIB (Management Information Base)
   • A database of all variables a device can report or change.
   • Example variables: Interface status, traffic counters, CPU load, memory usage.
2. OID (Object Identifier)
   • Each piece of information in the MIB has a unique numeric identifier called an OID.
   • Example: 1.3.6.1.2.1.1.3 could represent the system uptime of a router.

• NMS uses OIDs to query specific data from the managed device.

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6. Why SNMP is Important in Network Operations

SNMP is critical for network monitoring and management because it allows administrators to:

1. Monitor Network Health
   • Check CPU, memory, interface status, bandwidth usage, and device uptime.
2. Detect Problems Early
   • Receive alerts (TRAPs) when devices fail or thresholds are exceeded.
3. Perform Remote Management
   • Change configurations, reset interfaces, or update devices from a central location.
4. Automate Network Monitoring
   • SNMP can feed data to dashboards that visualize network performance and send automated alerts if something goes wrong.

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7. Typical SNMP Workflow in IT Networks

1. NMS sends a GET request to a router asking for interface status.
2. The router agent responds with the current status.
3. The NMS detects high CPU usage and sends a SET command to enable logging.
4. Later, the router sends a TRAP to NMS saying an interface went down.
5. Admin receives alert and can quickly take action.

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8. CCNA Exam Key Points

• SNMP purpose: Monitor and manage network devices.
• Main components: Managed device, SNMP agent, NMS.
• PDUs/messages: GET, SET, TRAP.
• Versions: SNMPv1, SNMPv2c (plain text), SNMPv3 (secure).
• Data structure: MIB stores data, OIDs identify data items.
• Benefits: Monitoring, alerts, automation, remote management.

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✅ Tip for remembering SNMP for the exam:

• Think “NMS asks questions (GET), gives commands (SET), and devices shout alerts (TRAP)”.

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