CompTIA Network+ (N10-009) Fact Sheet Quick Reference Exam Code: N10-009 Duration: 90 minutes Questions: Up to 90 (MCQ + performance-based) Passing Score: 720/900 Cost: $369 USD Validity: 3 years Delivery: Pearson VUE (testing center or online proctored)
Exam Domain Breakdown Domain Weight Focus Networking Concepts 23% OSI, ports/protocols, IP addressing, subnetting, services, topologies Network Implementation 20% Routing, switching, VLANs, STP, wireless Network Operations 19% Documentation, monitoring, DR/BCP, organizational docs Network Security 14% Threats, hardening, security devices, AAA, physical Network Troubleshooting 24% Methodology, CLI/hardware tools, common issues
OSI Model Layer Name PDU Devices Examples 7 Application Data - HTTP, HTTPS, FTP, SMTP, DNS, DHCP, SNMP 6 Presentation Data - TLS/SSL encryption, JPEG, ASCII, MIME 5 Session Data - NetBIOS, RPC, PPTP, session establishment 4 Transport Segment (TCP) / Datagram (UDP) - TCP, UDP, ports 3 Network Packet Router, Layer 3 switch IP, ICMP, IPsec, OSPF, BGP, EIGRP 2 Data Link Frame Switch, bridge, NIC, AP Ethernet, MAC, ARP, 802.1Q, STP, PPP 1 Physical Bits Hub, repeater, cable, transceiver Copper, fiber, wireless RF, RJ-45
Mnemonic (top to bottom): All People Seem To Need Data Processing Mnemonic (bottom to top): Please Do Not Throw Sausage Pizza Away
TCP/IP model mapping: - Application (OSI 5-7) -> HTTP, DNS, etc. - Transport (OSI 4) -> TCP/UDP - Internet (OSI 3) -> IP, ICMP - Link / Network Access (OSI 1-2) -> Ethernet, Wi-Fi
Common Ports and Protocols Memorize these for the exam Port Protocol TCP/UDP Purpose 20 FTP-Data TCP FTP data channel 21 FTP TCP FTP control channel 22 SSH / SCP / SFTP TCP Secure shell, secure copy, secure FTP 23 Telnet TCP Insecure remote shell 25 SMTP TCP Mail submission/relay 53 DNS TCP/UDP Name resolution (UDP for queries, TCP for zone transfer / >512 byte) 67 DHCP server UDP DHCP server listens here 68 DHCP client UDP DHCP client listens here 69 TFTP UDP Trivial FTP, no auth 80 HTTP TCP Web (cleartext) 88 Kerberos TCP/UDP Authentication 110 POP3 TCP Email retrieval 119 NNTP TCP Network news 123 NTP UDP Time synchronization 137-139 NetBIOS TCP/UDP Legacy Windows networking 143 IMAP TCP Email retrieval (server-side folders) 161 SNMP UDP Network management agent 162 SNMP trap UDP Asynchronous SNMP notification 389 LDAP TCP/UDP Directory services (cleartext) 443 HTTPS TCP HTTP over TLS 445 SMB TCP Windows file sharing (modern) 465 SMTPS (legacy) TCP SMTP over TLS (implicit) 514 Syslog UDP Centralized logging 587 SMTP submission TCP Authenticated mail submission with STARTTLS 636 LDAPS TCP LDAP over TLS 989/990 FTPS TCP FTP over TLS (data/control) 993 IMAPS TCP IMAP over TLS 995 POP3S TCP POP3 over TLS 1433 MS SQL TCP Microsoft SQL Server 1521 Oracle DB TCP Oracle database 1645/1646 RADIUS (legacy) UDP Older RADIUS ports 1701 L2TP UDP Layer 2 Tunneling Protocol 1720 H.323 TCP VoIP signaling 1812/1813 RADIUS UDP Authentication / accounting 3306 MySQL TCP MySQL database 3389 RDP TCP/UDP Remote Desktop Protocol 5060 SIP TCP/UDP VoIP signaling (cleartext) 5061 SIP-TLS TCP SIP over TLS 5432 PostgreSQL TCP PostgreSQL database 5900 VNC TCP Virtual Network Computing 6514 Syslog over TLS TCP Encrypted syslog 8080 HTTP-alt TCP Common alternate web port (proxies)
Tricky pairs to remember Insecure Port Secure equivalent Port FTP 21 SFTP / FTPS 22 / 989-990 Telnet 23 SSH 22 HTTP 80 HTTPS 443 SMTP 25 SMTPS / submission+TLS 465 / 587 LDAP 389 LDAPS 636 POP3 110 POP3S 995 IMAP 143 IMAPS 993 SNMPv1/v2c 161 SNMPv3 161 DNS 53 DNS over TLS / DoH 853 / 443
IPv4 Addressing Address Classes (legacy classful, still tested) Class First Octet Default Mask CIDR Hosts per network A 1-126 255.0.0.0 /8 16,777,214 B 128-191 255.255.0.0 /16 65,534 C 192-223 255.255.255.0 /24 254 D 224-239 - - Multicast E 240-255 - - Reserved/experimental
127.0.0.0/8 is loopback (not Class A in practice).
Private (RFC 1918) Range Mask CIDR 10.0.0.0 - 10.255.255.255 255.0.0.0 10.0.0.0/8 172.16.0.0 - 172.31.255.255 255.240.0.0 172.16.0.0/12 192.168.0.0 - 192.168.255.255 255.255.0.0 192.168.0.0/16
Other reserved ranges Range Purpose 127.0.0.0/8 Loopback 169.254.0.0/16 APIPA / link-local (DHCP failure) 100.64.0.0/10 Carrier-grade NAT (RFC 6598) 224.0.0.0/4 Multicast 0.0.0.0/8 "This network" / default route prefix 255.255.255.255 Limited broadcast
Subnetting Cheat Sheet Powers of 2 Bits Value Bits Value 1 2 9 512 2 4 10 1,024 3 8 11 2,048 4 16 12 4,096 5 32 13 8,192 6 64 14 16,384 7 128 15 32,768 8 256 16 65,536
CIDR / mask / hosts (most common) CIDR Subnet Mask Wildcard Host bits Total IPs Usable hosts /16 255.255.0.0 0.0.255.255 16 65,536 65,534 /20 255.255.240.0 0.0.15.255 12 4,096 4,094 /22 255.255.252.0 0.0.3.255 10 1,024 1,022 /23 255.255.254.0 0.0.1.255 9 512 510 /24 255.255.255.0 0.0.0.255 8 256 254 /25 255.255.255.128 0.0.0.127 7 128 126 /26 255.255.255.192 0.0.0.63 6 64 62 /27 255.255.255.224 0.0.0.31 5 32 30 /28 255.255.255.240 0.0.0.15 4 16 14 /29 255.255.255.248 0.0.0.7 3 8 6 /30 255.255.255.252 0.0.0.3 2 4 2 /31 255.255.255.254 0.0.0.1 1 2 2 (point-to-point, RFC 3021) /32 255.255.255.255 0.0.0.0 0 1 1 (host route)
Formula: Usable hosts = 2^(host bits) - 2 (network and broadcast addresses). Exception: /31 used for point-to-point links per RFC 3021 has 2 usable.
Magic number trick For a given /N mask, the "magic number" is 256 - last non-zero octet of the mask. Subnet boundaries fall on multiples of the magic number in that octet.
Example: 192.168.1.100/26 - Mask = 255.255.255.192, magic number = 256 - 192 = 64 - Subnets in fourth octet: .0, .64, .128, .192 - 100 falls in .64 subnet -> network 192.168.1.64, broadcast 192.168.1.127, usable .65 - .126
IPv6 128 bits, written as 8 groups of 4 hex digits separated by colons Leading zeros in a group can be dropped: 2001:0db8:0000:0000:0000:0000:0000:0001 -> 2001:db8::1 Double colon :: collapses one run of consecutive zero groups (only once per address) Address Types Prefix Type Notes 2000::/3Global unicast Internet-routable, equivalent to public IPv4 fc00::/7Unique local (ULA) Equivalent to RFC 1918 private fe80::/10Link-local Auto-assigned per interface, never routed ff00::/8Multicast No broadcast in IPv6 ::1/128Loopback Equivalent to 127.0.0.1 ::/128Unspecified Equivalent to 0.0.0.0 2001:db8::/32Documentation Use in examples
Address assignment SLAAC - Stateless Address Autoconfig: derives address from prefix + interface ID (EUI-64 or random)DHCPv6 - Stateful, similar to DHCPv4EUI-64 - Builds last 64 bits from 48-bit MAC: split MAC, insert ff:fe in middle, flip 7th bit Key differences from IPv4 No broadcast (uses multicast) No NAT typically (every host is globally addressable) Built-in IPsec support (originally mandatory, now recommended) Neighbor Discovery Protocol (NDP) replaces ARP, uses ICMPv6 No fragmentation by routers (only by source) Cable Types and Standards Twisted Pair Copper Category Max Speed Max Distance Frequency Common use Cat 3 10 Mbps 100 m 16 MHz Legacy phone, 10BASE-T Cat 5 100 Mbps 100 m 100 MHz 100BASE-TX (Fast Ethernet) Cat 5e 1 Gbps 100 m 100 MHz 1000BASE-T (Gigabit), most common legacy Cat 6 1 Gbps (10 Gbps to 55 m) 100 m / 55 m for 10G 250 MHz Modern enterprise Cat 6a 10 Gbps 100 m 500 MHz 10GBASE-T full distance Cat 7 10 Gbps 100 m 600 MHz Shielded, less common Cat 8 25/40 Gbps 30 m 2000 MHz Data center top-of-rack
Shielding codes: UTP (unshielded), STP / FTP (shielded/foiled), S/FTP (overall braid + foiled pairs).
Fiber Type Mode Wavelength Max Distance Color jacket OM1 Multi-mode 62.5/125 850/1300 nm 33 m at 10G Orange OM2 Multi-mode 50/125 850/1300 nm 82 m at 10G Orange OM3 Multi-mode 50/125 (laser optimized) 850 nm 300 m at 10G Aqua OM4 Multi-mode 50/125 850 nm 400 m at 10G Aqua / erika violet OM5 Multi-mode wideband 850-953 nm 400 m at 10G, supports SWDM Lime green OS1 Single-mode 1310/1550 nm ~10 km Yellow OS2 Single-mode 1310/1550 nm ~40+ km Yellow
Connector types: LC (small form, common in data centers), SC (square push-pull), ST (bayonet, legacy), MTRJ, MPO/MTP (ribbon, multi-fiber), FC (screw-on).
Ethernet Standards Standard Speed Media Max Distance 10BASE-T 10 Mbps Cat 3+ 100 m 100BASE-TX 100 Mbps Cat 5+ 100 m 1000BASE-T 1 Gbps Cat 5e+ 100 m 1000BASE-SX 1 Gbps MMF 220-550 m 1000BASE-LX 1 Gbps SMF 5 km 10GBASE-T 10 Gbps Cat 6a/7 100 m (Cat 6 to 55 m) 10GBASE-SR 10 Gbps MMF 300-400 m 10GBASE-LR 10 Gbps SMF 10 km 40GBASE-SR4 40 Gbps MMF (MPO) 100-150 m 100GBASE-SR4 100 Gbps MMF (MPO) 70-100 m
Wiring Standard Pin pairs Use case T568A Green/white-green / orange/white-orange / blue/white-blue / brown/white-brown Residential (older), US gov T568B Orange/white-orange / green/white-green / blue/white-blue / brown/white-brown Most common in commercial Straight-through Same standard both ends (B-B or A-A) Host-to-switch, switch-to-router Crossover A on one end, B on other Same-device-type connection (legacy; modern Auto-MDIX makes obsolete) Rollover (console) Reversed pin order Cisco console cable
Wireless 802.11 Standards Standard Wi-Fi name Frequency Max Speed (theoretical) MIMO 802.11a - 5 GHz 54 Mbps No 802.11b - 2.4 GHz 11 Mbps No 802.11g - 2.4 GHz 54 Mbps No 802.11n Wi-Fi 4 2.⅘ GHz 600 Mbps Yes (4x4) 802.11ac Wi-Fi 5 5 GHz 6.9 Gbps MU-MIMO (DL) 802.11ax Wi-Fi 6 / 6E 2.⅘/6 GHz 9.6 Gbps MU-MIMO (UL+DL), OFDMA 802.11be Wi-Fi 7 2.⅘/6 GHz 46 Gbps 320 MHz channels, MLO
Channels to know: - 2.4 GHz: only channels 1, 6, 11 are non-overlapping in North America (each 22 MHz wide) - 5 GHz: many non-overlapping 20 MHz channels; some require DFS (Dynamic Frequency Selection) due to radar - 6 GHz: 7 non-overlapping 80 MHz or 14 non-overlapping 40 MHz channels (Wi-Fi 6E)
Wireless Security Standard Encryption Authentication Notes WEP RC4 (broken) Static key Deprecated, never use WPA TKIP PSK or 802.1X Legacy, broken WPA2 AES-CCMP PSK or 802.1X Long-time standard, KRACK vulnerable WPA3 AES-GCMP-256 (Enterprise) / SAE SAE (Personal), 802.1X+SuiteB (Enterprise) Current, mandatory PMF
802.1X / EAP variants: - EAP-TLS - Mutual cert-based, strongest, requires client certs - EAP-TTLS - Server cert + tunneled inner auth - PEAP - Server cert + tunneled MS-CHAPv2 (most common Windows) - EAP-FAST - Cisco, uses PAC instead of cert - LEAP - Cisco legacy, broken, do not use
Routing Administrative Distance (Cisco defaults) Source AD Connected interface 0 Static route 1 EBGP 20 EIGRP (internal) 90 OSPF 110 IS-IS 115 RIP 120 EIGRP (external) 170 IBGP 200 Unknown / unreachable 255
Routing Protocol Comparison Protocol Type Algorithm Metric Open/Proprietary RIP / RIPv2 Distance vector Bellman-Ford Hop count (max 15) Open OSPF Link state Dijkstra SPF Cost (bandwidth-based) Open EIGRP Advanced distance vector / hybrid DUAL Composite (BW, delay) Open (was Cisco-only) IS-IS Link state Dijkstra SPF Cost Open (ISP backbone) BGP Path vector Best path selection AS-path + attributes Open (internet routing)
Switching Spanning Tree Protocol (STP) Standard Name Convergence 802.1D STP 30-50 sec 802.1w RSTP (Rapid STP) <10 sec 802.1s MSTP (Multiple STP) Per VLAN group Cisco PVST+ Per-VLAN STP One instance per VLAN
Port states (RSTP): Discarding, Learning, Forwarding (legacy STP also had Listening, Blocking). Port roles: Root, Designated, Alternate, Backup.
Protections: BPDU Guard (disables port if BPDU received on access port), Root Guard (prevents downstream switch from becoming root), Loop Guard, PortFast (skip listening/learning on access ports).
VLAN and Trunking 802.1Q - Industry standard VLAN tagging, inserts 4-byte tag (TPID 0x8100 + 12-bit VLAN ID)Native VLAN - Untagged traffic on a trunk; default VLAN 1 (security best practice: change to unused VLAN)VLAN range - 1-4094 (12 bits); 1, 1002-1005 reserved on CiscoVoice VLAN - Separate VLAN for IP phones, often via CDP/LLDP-MED auto-configVTP - Cisco VLAN Trunking Protocol; modes server/client/transparent Link Aggregation LACP (802.3ad) - Industry standard, active or passive negotiationPAgP - Cisco proprietary, modes auto/desirableStatic / "on" - No negotiation, both sides must match exactly Network Services DHCP Process (DORA) Discover - Client broadcasts DHCPDISCOVER (src 0.0.0.0, dst 255.255.255.255, UDP 67)Offer - Server replies with DHCPOFFER (proposed lease)Request - Client broadcasts DHCPREQUEST for chosen offerAcknowledge - Server confirms with DHCPACK DHCP relay / IP helper: Forwards broadcast DHCP requests across subnets to a central DHCP server. Reservation: Specific IP tied to a MAC address. Exclusion: IP excluded from the pool. Lease time: How long client can use the address before renewing.
DNS Record Types Record Purpose A Hostname -> IPv4 AAAA Hostname -> IPv6 CNAME Alias to another name MX Mail exchanger (priority) NS Authoritative name server for zone SOA Start of authority (zone metadata) PTR Reverse: IP -> hostname TXT Arbitrary text (SPF, DKIM, domain verification) SRV Service location (used by AD, SIP) CAA Authorized certificate issuers
DNS hierarchy: Root (.) -> TLD (.com) -> Domain (example.com) -> Subdomain (www.example.com). Recursive resolver asks on behalf of the client; authoritative server holds the actual records.
Other services Service Purpose Port NTP Time sync (stratum 0 = atomic clock; stratum 16 = unsynced) UDP 123 SNMP Network monitoring; v1/v2c use community strings, v3 adds auth + encryption UDP 161, traps 162 Syslog Centralized logging; severities 0-7 (Emergency to Debug) UDP 514 NetFlow / sFlow / IPFIX Flow telemetry for traffic analysis UDP (varies)
Command Reference Windows / Linux equivalents Task Windows Linux/macOS Show IP config ipconfig /allip addr / ifconfig Renew DHCP ipconfig /renewdhclient -r && dhclient Flush DNS ipconfig /flushdnssystemd-resolve --flush-caches / dscacheutil -flushcache (macOS) Test reachability pingping Trace route tracerttraceroute (UDP) / traceroute -I (ICMP) Combined ping+trace pathpingmtr Show routing table route print / netstat -rip route / route -n Show ARP cache arp -aip neigh / arp -a Show connections netstat -anoss -tunap / netstat -tunap DNS lookup nslookupdig / host / nslookup Capture packets pktmon (Win10+)tcpdump Port scan nmapnmap Bandwidth test iperf3iperf3
Quick examples ping -c 4 8.8.8.8 # Linux: 4 echo requests
ping -n 4 8.8.8.8 # Windows: 4 echo requests
tracert -d www.example.com # No reverse DNS, faster
traceroute -I 8.8.8.8 # Use ICMP instead of UDP
dig example.com MX +short # Just the MX records
nslookup -type=AAAA example.com # Query IPv6 record
ip -br addr # Linux: brief interface summary
ss -tlnp # Linux: listening TCP sockets with PIDs
netstat -anob # Windows: ports + binary owning them
nmap -sS -p 22,80,443 10.0.0.0/24 # SYN scan three ports across subnet
tcpdump -ni eth0 host 1.2.3.4 and port 53
Tool Purpose Cable tester Verify continuity, pinout, identify breaks Tone generator + probe (fox and hound) Trace cable runs through walls/bundles OTDR Optical Time-Domain Reflectometer - measures fiber length, finds breaks/bends Light meter / OPM Measure optical power on fiber Multimeter Voltage, continuity, resistance Loopback adapter / plug Test NIC port functionality Wi-Fi analyzer Survey channels, signal strength, interference, AP placement Spectrum analyzer Identify non-Wi-Fi RF interference (microwaves, baby monitors) Punch-down tool (110/66) Terminate cables on patch panels and 110/66 blocks Crimper Attach RJ-45/RJ-11 connectors Cable certifier Verify Cat 5e/6/6a meets standard for distance, attenuation, NEXT Protocol analyzer Wireshark or hardware tap to capture frames
Troubleshooting Methodology (CompTIA 7-step) Identify the problem - Gather info, question users, identify symptoms, determine if multiple problems, document approach + scopeEstablish a theory of probable cause - Question the obvious, consider OSI bottom-upTest the theory - If confirmed, plan next steps; if not, re-establish theory or escalateEstablish a plan of action - Document fix, identify potential side effectsImplement the solution - Or escalate as necessaryVerify full system functionality - Implement preventive measuresDocument findings, actions, outcomes - Update KB, runbook, change log High-Yield Memorizables CIA in networking Confidentiality - Encryption (IPsec, TLS), VLAN segmentation, ACLsIntegrity - Hashing in IPsec/TLS, port security, DAIAvailability - Redundancy (HSRP/VRRP, link agg, dual-homing), DDoS protection Acronyms cheat sheet APIPA - Automatic Private IP Addressing (169.254.0.0/16)CIDR - Classless Inter-Domain RoutingVLSM - Variable Length Subnet MaskingNAT/PAT - Network/Port Address TranslationVLAN - Virtual LANVPN - Virtual Private NetworkMTU - Maximum Transmission Unit (default 1500 Ethernet)MSS - Maximum Segment Size (typically MTU - 40)PoE - Power over Ethernet (802.3af 15.4W, at 30W, bt 60-100W)HSRP / VRRP / GLBP - First-hop redundancy (Cisco / open / Cisco load balancing)SDN / SD-WAN - Software-Defined Networking / Wide Area NetworkNFV - Network Function VirtualizationCASB - Cloud Access Security BrokerSASE - Secure Access Service EdgeZTNA - Zero Trust Network Access Documentation Good luck on your exam! Network+ rewards memorization of ports, masks, and tools combined with the OSI bottom-up reflex on every troubleshooting scenario.