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CompTIA Network+ Cheat Sheet

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Networking Concepts

  • 23% of exam
  • OSI Layers Ports Addressing Media Cloud Models

Network Implementation

  • 20% of exam
  • Routing Switching Wireless Services Implementation Picker

Network Operations

  • 19% of exam
  • Monitoring Documentation Change Control Resilience Operations Picker

Network Security

  • 14% of exam
  • Security Controls Attack Cues AAA Segmentation IDS vs IPS

Network Troubleshooting

  • 24% of exam
  • Methodology Troubleshooting Tools Symptom Cues Wireless Troubleshooting Tool Picker

Quick Facts

  • Exam N10-009
  • Credential Network+
  • Time 90 min
  • Questions Max 90
  • Format MCQ + PBQ
  • Pass 720/900
  • Launch Jun 20 2024
  • Experience A+ + 9-12 mo

OSI Order CO

  • Please Do Not Throw Sausage Pizza Away
  • Physical Data Link Network Transport Session Presentation Application

TCP vs UDP CO

TCP

  • Connection-oriented
  • Reliable delivery
  • Handshake

UDP

  • Connectionless
  • Low overhead
  • No delivery guarantee
  • Reliability vs speed

Protocol Picker CO

  • Secure shell → SSH ( TCP 22 )
  • Secure file transfer → SFTP ( TCP 22 )
  • Plain file transfer → FTP ( 20/21 )
  • Name resolution → DNS ( 53 )
  • Address leasing → DHCP ( 67/68 )
  • Encrypted web → HTTPS ( 443 )
  • Remote desktop → RDP ( 3389 )
  • Device polling → SNMP ( 161 )

OSI Layers CO

  • L1 Physical Bits and media
  • L2 Data Link Frames and MACs
  • L3 Network IP routing
  • L4 Transport TCP/UDP ports
  • L5 Session Dialog control
  • L6 Presentation Format/encryption
  • L7 Application User services

Private IPv4 CO

  • Private ranges: ten, seventeen, one-ninety-two
  • 10/8 172.16/12 192.168/16

Ports CO

  • FTP 20/21 Plain file transfer
  • SFTP 22 SSH file transfer
  • SSH 22 Secure shell
  • Telnet 23 Plain remote shell
  • SMTP 25 Mail send
  • DNS 53 Name resolution
  • DHCP 67/68 Address leasing
  • HTTP 80 Plain web
  • HTTPS 443 Encrypted web
  • SNMP 161 Device monitoring
  • LDAP 389 Directory queries
  • LDAPS 636 Secure directory
  • RDP 3389 Remote desktop
  • NTP 123 Time sync
  • SIP 5060 Voice signaling
  • TFTP 69 Plain UDP transfer

Addressing CO

  • 10.0.0.0/8 Private IPv4
  • 172.16.0.0/12 Private IPv4
  • 192.168.0.0/16 Private IPv4
  • 169.254.0.0/16 APIPA
  • 127.0.0.1 Loopback
  • FE80::/10 IPv6 link-local
  • 2000::/3 IPv6 global
  • FF00::/8 IPv6 multicast
  • ::1 IPv6 loopback
  • /30 Two usable hosts
  • /27 Thirty usable hosts
  • VLSM Variable subnet sizing

Media CO

  • Cat 5e Gigabit copper
  • Cat 6 Higher-speed copper
  • Cat 6A 10G copper
  • SMF Long-distance fiber
  • MMF Shorter fiber
  • DAC Short data-center link
  • Coax Broadband RF media
  • RJ45 Twisted-pair Ethernet
  • LC Common fiber connector
  • MPO High-density fiber

Wireless Bands IM

  • 2.4 reaches; 5 speeds; 6 clears
  • 2.4 = range 5 = capacity 6 = clean

Switch vs Router IM

Switch

  • Layer 2
  • MAC forwarding
  • Same VLAN

Router

  • Layer 3
  • IP forwarding
  • Between networks
  • Frames vs packets

Implementation Picker IM

  • Separate broadcasts → VLAN ( Layer 2 )
  • Route VLANs → SVI ( Layer 3 )
  • Avoid switch loops → STP ( Blocks path )
  • Bundle links → LACP ( Port channel )
  • Share public IP → PAT ( Overload )
  • Gateway failover → FHRP ( VIP )
  • Mix WAN links → SD-WAN ( Path control )
  • Private carrier WAN → MPLS ( Provider core )

Routing + Switching IM

  • Static route Manual path
  • OSPF Link-state IGP
  • EIGRP Advanced distance vector
  • BGP Path-vector EGP
  • NAT Address translation
  • PAT Port overload
  • FHRP Gateway redundancy
  • VLAN Broadcast segmentation
  • Trunk Tagged VLAN link
  • Access port Single VLAN
  • STP Loop prevention
  • LACP Link aggregation

VLAN vs Subnet IM

VLAN

  • Layer 2 segment
  • Broadcast boundary
  • Switch config

Subnet

  • Layer 3 range
  • IP boundary
  • Router config
  • Segmentation layers differ

Wireless IM

  • 802.11n Wi-Fi 4
  • 802.11ac Wi-Fi 5
  • 802.11ax Wi-Fi 6/6E
  • 2.4 GHz Range; interference
  • 5 GHz More channels
  • 6 GHz Clean spectrum
  • SSID Network name
  • WPA3 Modern Wi-Fi security
  • Captive portal Guest onboarding
  • Site survey RF planning

DNS vs DHCP IM

DNS

  • Names to addresses
  • Records
  • Resolver clues

DHCP

  • Leases addresses
  • Options
  • Scope clues
  • Names vs leases

Services IM

  • A Name to IPv4
  • AAAA Name to IPv6
  • CNAME Alias record
  • MX Mail exchanger
  • TXT Text metadata
  • SRV Service location
  • DHCP scope Address pool
  • Reservation Fixed DHCP lease
  • Relay DHCP across subnets
  • NTS Secure time sync

Operations Picker OP

  • Track devices → Inventory ( Ownership )
  • Track addresses → IPAM ( Subnets )
  • Know normal → Baseline ( Compare )
  • Collect events → Syslog ( Logs )
  • View conversations → NetFlow ( Traffic )
  • Inspect packets → Capture ( Evidence )
  • Limit outage → RTO ( Time )
  • Limit data loss → RPO ( Data )

Monitoring OP

  • SNMP Polls and traps
  • NetFlow Traffic conversations
  • Syslog Central event logs
  • SIEM Security log correlation
  • Packet capture Actual traffic evidence
  • Port mirror Copy switch traffic
  • Baseline Known normal
  • API Automation interface
  • IPAM Address management
  • Runbook Repeatable procedure

Resilience + Docs OP

  • RPO Acceptable data loss
  • RTO Acceptable downtime
  • MTTR Repair time
  • MTBF Failure interval
  • Hot site Ready recovery site
  • Warm site Partially ready site
  • Cold site Space and utilities
  • SLA Service commitment
  • EOL Lifecycle ending
  • Config backup Restore device state

MFA Factors SE

  • Know, have, are: MFA needs variety
  • Password Token Biometric

IDS vs IPS SE

IDS

  • Detects
  • Alerts
  • Out-of-band

IPS

  • Blocks
  • Inline
  • Drops traffic
  • Alert vs block

Security Controls SE

  • ACL Traffic allow/deny
  • Firewall Policy enforcement
  • NGFW App-aware firewall
  • IDS Detect and alert
  • IPS Inline blocking
  • NAC Access posture checks
  • 802.1X Port authentication
  • RADIUS AAA for access
  • TACACS+ Device admin AAA
  • MFA Multiple factor types
  • PKI Certificate trust
  • Zero Trust Verify every access

Stateful vs Stateless SE

Stateful

  • Tracks sessions
  • Return traffic aware
  • Context checks

Stateless

  • Packet rules
  • No session memory
  • Fast filtering
  • Context vs rules

Attack Cues SE

  • DDoS Availability flood
  • ARP spoofing False MAC mapping
  • DNS poisoning Bad name answers
  • VLAN hopping Escapes segmentation
  • MAC flooding Overflows CAM table
  • Evil twin Rogue Wi-Fi AP
  • On-path Intercepts traffic
  • Phishing Deceptive messages
  • Tailgating Unauthorized following
  • Honeypot Decoy system

RADIUS vs TACACS+ SE

RADIUS

  • Access AAA
  • UDP common
  • Wireless/VPN

TACACS+

  • Admin AAA
  • TCP
  • Command authorization
  • Access vs admin

Troubleshooting Flow TR

  • Identify, theorize, test, plan, fix, verify, document
  • Identify Theory Test Plan Implement Verify Document

Latency vs Jitter TR

Latency

  • Delay
  • Round-trip time
  • Slow response

Jitter

  • Delay variation
  • Voice distortion
  • Video stutter
  • Delay vs variation

Tool Picker TR

  • No link light → Cable tester ( Layer 1 )
  • Fiber distance fault → OTDR ( Optical )
  • Names fail → nslookup ( DNS )
  • Path stops → traceroute ( Hops )
  • Ports unknown → netstat ( Sockets )
  • Wi-Fi noise → Wi-Fi analyzer ( RF )
  • Packet proof → Wireshark ( Frames )
  • Route choice → Route table ( Prefix )

Troubleshooting Tools TR

  • ping ICMP reachability
  • traceroute Path hops
  • nslookup DNS queries
  • dig Detailed DNS
  • ipconfig Windows IP config
  • ifconfig Unix interface config
  • ip Linux networking
  • arp IP-to-MAC cache
  • netstat Connections and ports
  • ss Socket statistics
  • Wireshark Packet analysis
  • OTDR Fiber fault distance

Symptom Cues TR

  • No link Physical first
  • APIPA DHCP failed
  • Names fail Check DNS
  • Gateway works Local path ok
  • Off-net fails Gateway/routing issue
  • CRC errors Cable/duplex issue
  • Runts Undersized frames
  • Giants Oversized frames
  • High jitter Voice/video impact
  • Packet loss Drops/retransmissions
  • Weak RSSI Poor signal
  • Low SNR Noisy RF

Common Traps

Ping Passing

  • ICMP works ≠ Service may fail

DNS Failure

  • Names fail ≠ IP may work

APIPA Cause

  • DHCP failed ≠ Cable not proven

Route Choice

  • Most specific wins ≠ Default route last

SSID Hiding

  • Name still visible ≠ Not real security

Trunk Ports

  • Tags many VLANs ≠ Access uses one

Process Order

  • Test theory first ≠ Then implement plan

Last Minute

  • 1. Weights: 23/20/19/14/24
  • 2. Troubleshooting is largest domain
  • 3. Longest prefix wins routes
  • 4. DNS names; DHCP leases
  • 5. APIPA means DHCP failed
  • 6. VLAN separates broadcasts
  • 7. Trunk tags multiple VLANs
  • 8. STP blocks Layer 2 loops
  • 9. IDS alerts; IPS blocks
  • 10. Document after verifying fix
  • 11. PBQs: read task first
  • 12. Secure management beats Telnet

CompTIA Network+

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