3.1 Explain the purpose of organizational processes and procedures

Documentation

📘CompTIA Network+ (N10-009)

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Network diagrams are visual documents that show how devices, connections, and data flows exist inside a network. They help technicians understand the structure of a network quickly and accurately.

On the exam, network diagrams are grouped into three levels based on the OSI model:

• Layer 1 diagrams (Physical diagrams)
• Layer 2 diagrams (Data Link diagrams)
• Layer 3 diagrams (Network diagrams)

Each type provides a different level of detail and is used for specific purposes in IT operations.

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1. Layer 1 Network Diagrams (Physical Diagrams)

What They Show

Layer 1 diagrams show the actual physical layout of the network. They include:

• Physical devices
  • Switches
  • Routers
  • Servers
  • Firewalls
  • Patch panels
  • Access points
• Physical cables and ports
  • Copper (Ethernet) cables
  • Fiber cables
  • Patch panel connections
  • Port numbers (e.g., Gi0/1, 1/0/24)
• Hardware location
  • Room numbers
  • Rack positions
  • Rack units (U numbers)

Purpose

• Helps technicians trace physical cables
• Useful for hardware installation and replacement
• Supports troubleshooting when a cable, port, or device fails
• Shows exactly “what is connected to what”

When Used

• During new hardware deployment
• During physical inspections
• When replacing a switch, router, or server
• When identifying incorrect cabling or loose connections

Why It’s Important for the Exam

Network+ expects you to understand that Layer 1 diagrams = physical network layout with cables, ports, and device locations.

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2. Layer 2 Network Diagrams (Data Link Diagrams)

What They Show

Layer 2 diagrams explain how network switches and Layer 2 technologies operate. They include:

• Switch-to-switch relationships
• VLANs (Virtual LANs)
• Trunk ports
  • e.g., 802.1Q trunks
• Access ports
• STP (Spanning Tree Protocol) paths
• MAC address flows
• Switch stacking or chassis connections

Purpose

• Helps understand broadcast domains
• Shows how users are separated into VLANs
• Helps troubleshoot issues like:
  • VLAN misconfiguration
  • Loops in the network
  • Incorrect tagging or trunking
• Shows paths used by STP for preventing loops

When Used

• When configuring VLANs
• When diagnosing broadcast storms
• When verifying trunk configurations
• When adding a new switch into the existing network design

Why It’s Important for the Exam

Network+ wants you to understand that Layer 2 diagrams focus on switching, VLANs, and data-link paths, not physical cabling.

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3. Layer 3 Network Diagrams (Network Diagrams)

What They Show

Layer 3 diagrams focus on IP-based communication across networks. They include:

• Routers
• Layer 3 switches
• Firewalls
• Routing paths
• Subnets and IP ranges
• WAN links
  • MPLS
  • VPN tunnels
  • SD-WAN connections
• Default gateways
• Network segmentation
• ACL boundaries (high-level)

Purpose

• Shows how traffic moves between networks
• Helps design and troubleshoot routing issues
• Useful for identifying incorrect gateways or IP addressing problems
• Provides a high-level overview of the network’s structure

When Used

• When designing a new network
• When troubleshooting routing failures
• When setting up new subnets
• When creating redundant paths for high availability

Why It’s Important for the Exam

Layer 3 diagrams help you understand logical traffic flow, routing decisions, and IP topology, which are core topics in Network+.

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Differences Between Layer 1, Layer 2, and Layer 3 Diagrams

Diagram Type	Focus	Shows	Used For
Layer 1 (Physical)	Hardware	Cables, ports, racks, physical layout	Hardware installation, cable tracing
Layer 2 (Data Link)	Switching	VLANs, trunks, STP, switch paths	VLAN issues, broadcast problems, loop prevention
Layer 3 (Network)	Routing	Subnets, routers, gateways, IP paths	Routing issues, subnet design, WAN planning

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How Network Diagrams Are Used in IT Environments

1. Troubleshooting

A technician may use:

• Layer 1 to find a bad cable
• Layer 2 to check if a VLAN is missing
• Layer 3 to fix a routing path

2. Change Management

Before modifying the network, diagrams show:

• What devices will be affected
• How traffic flows might change
• Where risks exist

3. Onboarding New Technicians

New staff can quickly understand the network structure using these diagrams.

4. Audits & Compliance

Documentation like network diagrams is often required by:

• Security audits
• Industry standards
• Internal IT policies

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Best Practices for Network Diagrams (Important for the Exam)

• Keep diagrams updated regularly
• Use standardized symbols (router, switch, firewall icons)
• Label everything clearly
  • VLAN IDs
  • Subnet IDs
  • Device names
  • Cable labels
• Separate diagrams by layer to avoid clutter
• Store diagrams centrally so the whole IT team can access them
• Protect diagrams because they contain sensitive network information

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Exam Tips

✔ Layer 1 = Physical connections
✔ Layer 2 = Switching, VLANs, broadcast domains
✔ Layer 3 = Routing, subnets, IP traffic flow
✔ Expect questions asking which type of diagram is best for a situation
✔ Know that diagrams help with troubleshooting, planning, and documenting changes