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CompTIA Network+· Exam reference card · 2026 · Edureify AI
CompTIA Network+

Network+ Cheat Sheet

Network+ Tests Troubleshooting Judgment, Not Protocol Memorization

Knowing what TCP/IP is won't pass you. Knowing when a routing loop vs. a VLAN misconfiguration causes connectivity failure will.

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Among the harder certs
Avg: Approximately 63–68%
Pass: 750 / 1000
Most candidates understand CompTIA Network+ concepts — and still fail. This exam tests how you apply knowledge under pressure.
Core Framework

OSI Model as a Troubleshooting Framework

Network+ troubleshooting questions require OSI-layer thinking. Always isolate the problem to the correct layer before proposing a fix. Bottom-up troubleshooting (Physical → Application) is the standard methodology.

  1. 01
    Layer 1 Physical — Cable, NIC, port, signal
  2. 02
    Layer 2 Data Link — MAC, switching, VLANs, STP
  3. 03
    Layer 3 Network — IP routing, subnetting, ACLs
  4. 04
    Layer 4 Transport — TCP/UDP, port numbers, sessions
  5. 05
    Layers 5-7 — Application, session, presentation issues
Scenario Traps

Wrong instinct vs correct approach

Two devices on the same switch can't communicate
✕ Wrong instinct

Check the routing table and default gateway

✓ Correct approach

This is a Layer 2 issue — check VLAN assignments, trunk port configuration, and MAC address table; routing is irrelevant for same-subnet communication

Network performance degrades only during business hours
✕ Wrong instinct

Suspect a hardware failure since it's intermittent

✓ Correct approach

Load-based degradation suggests bandwidth saturation — check interface utilization, QoS settings, and identify traffic-heavy applications during peak hours

A newly added switch causes network instability
✕ Wrong instinct

Check the new switch's IP configuration

✓ Correct approach

A new switch may have introduced a Layer 2 loop — verify STP is enabled, check for BPDU guards, and look for broadcast storm indicators

Quick Rules

Know these cold

  • ▸ Troubleshoot bottom-up — hysical → Data Link → Network before assuming application issues
  • ▸ Same subnet = Layer 2 problem; different subnets = Layer 3 problem
  • ▸ STP prevents loops — always check it when a new switch causes instability
  • ▸ Duplex mismatch causes late collisions and poor throughput — check both ends
  • ▸ DNS failure causes hostname resolution errors; IP connectivity still works
  • ▸ DHCP exhaustion causes 169.254.x.x APIPA addresses — check scope leases
  • ▸ 802.1Q is the VLAN tagging standard; native VLANs must be configured consistently
Self Check

Can you answer these without checking your notes?

In this scenario: "Two devices on the same switch can't communicate" — what should you do first?
This is a Layer 2 issue — check VLAN assignments, trunk port configuration, and MAC address table; routing is irrelevant for same-subnet communication
In this scenario: "Network performance degrades only during business hours" — what should you do first?
Load-based degradation suggests bandwidth saturation — check interface utilization, QoS settings, and identify traffic-heavy applications during peak hours
In this scenario: "A newly added switch causes network instability" — what should you do first?
A new switch may have introduced a Layer 2 loop — verify STP is enabled, check for BPDU guards, and look for broadcast storm indicators
Failure Patterns

Common Exam Mistakes — What candidates get wrong

Misdiagnosing Layer 2 vs. Layer 3 problems

Devices on the same subnet that can't communicate have a Layer 2 issue (VLAN, switch, MAC table). Devices on different subnets that can't communicate have a Layer 3 issue (routing, ACL, default gateway).

Confusing subnetting with supernetting

Subnetting divides a network into smaller segments; supernetting (CIDR aggregation) combines networks. Candidates apply subnetting when a routing aggregation scenario is presented.

Misidentifying half-duplex vs. full-duplex as a speed vs. collision issue

Half-duplex causes collisions; full-duplex eliminates them. A duplex mismatch between a switch port and a NIC causes late collisions and slow performance — not a speed setting issue.

Treating all wireless interference as a channel overlap issue

2.4GHz has 3 non-overlapping channels (1, 6, 11). Co-channel interference (same channel) and adjacent channel interference are different problems with different solutions.

Ignoring spanning tree when troubleshooting network loops

Broadcast storms and MAC table instability on switched networks point to STP issues. Candidates look for routing loops when the actual problem is a Layer 2 STP failure or misconfiguration.

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