KnowledgebaseNetworkingSystem Administration

Networking Quick Reference Cheat Sheet

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0 10 1 minute read

OSI Model (7 Layers)

LayerNamePurposeExamples
7ApplicationUser‑level network servicesHTTP, DNS, SMTP, FTP
6PresentationEncoding, encryption, compressionSSL/TLS, MIME
5SessionConnection managementRPC, NetBIOS, PPTP
4TransportEnd‑to‑end deliveryTCP, UDP
3NetworkRouting & addressingIP, ICMP, IGMP
2Data LinkMAC addressing, framingEthernet, PPP, 802.11
1PhysicalBits on the wireCopper, fiber, RF

TCP/IP Model (4 Layers)

LayerPurposeExamples
ApplicationProtocols & servicesHTTP, DNS, SSH, DHCP
TransportSegments/datagramsTCP, UDP, QUIC
InternetRoutingIPv4, IPv6, ICMP
Network AccessPhysical + linkEthernet, Wi‑Fi, PPP

Common Port Numbers

Well‑Known Ports

PortProtocolDescription
20/21FTPFile Transfer
22SSHSecure shell
23TelnetRemote terminal (insecure)
25SMTPEmail sending
53DNSName resolution
67/68DHCPIP assignment
69TFTPSimple file transfer
80HTTPWeb traffic
110POP3Email retrieval
123NTPTime sync
143IMAPEmail retrieval
161/162SNMPNetwork management
389LDAPDirectory services
443HTTPSSecure web
514SyslogLogging
587SMTP (submission)Authenticated email
636LDAPSSecure LDAP
993/995IMAPS/POP3SSecure email

Subnet Masks & CIDR

CIDRMaskHosts
/24255.255.255.0254
/25255.255.255.128126
/26255.255.255.19262
/27255.255.255.22430
/28255.255.255.24014
/29255.255.255.2486
/30255.255.255.2522
/32Single host1

Ethernet Standards (IEEE 802.3)

StandardSpeedMediumMax Distance
10BASE‑T10 MbpsCat3+100 m
100BASE‑TX100 MbpsCat5+100 m
1000BASE‑T1 GbpsCat5e+100 m
1000BASE‑SX1 GbpsMMF220–550 m
1000BASE‑LX1 GbpsSMF5–10 km
10GBASE‑T10 GbpsCat6a+100 m
10GBASE‑SR10 GbpsMMF26–400 m
10GBASE‑LR10 GbpsSMF10 km
10GBASE‑ER10 GbpsSMF40 km
40GBASE‑T40 GbpsCat830 m
100GBASE‑LR4100 GbpsSMF10 km
100GBASE‑ER4100 GbpsSMF40 km

Cable Types & Max Distances

Twisted Pair

CategoryMax SpeedMax Distance
Cat5e1 Gbps100 m
Cat61–10 Gbps55 m (10G)
Cat6a10 Gbps100 m
Cat7/7a10–40 Gbps100 m
Cat825–40 Gbps30 m

Fiber

TypeModeDistance
OM1MMF275–550 m
OM2MMF550 m
OM3MMF300 m (10G)
OM4MMF400 m (10G)
OS1/OS2SMF10–40+ km

Fiber Connector Types

ConnectorTypeNotes
LCDuplexMost common modern connector
SCDuplexOlder but still widely used
STSingleLegacy twist‑lock
MPO/MTPMulti‑fiberUsed for 40G/100G

Wireless Standards (802.11)

StandardFrequencyMax Speed
802.11b2.4 GHz11 Mbps
802.11g2.4 GHz54 Mbps
802.11n2.4/5 GHz600 Mbps
802.11ac5 GHz1.3 Gbps+
802.11ax (Wi‑Fi 6)2.4/5 GHz9.6 Gbps
802.11be (Wi‑Fi 7)2.4/5/6 GHz30+ Gbps

Common Networking Commands

Windows

  • ipconfig /all — full IP configuration
  • ping <host> — connectivity test
  • tracert <host> — route path
  • netstat -ano — active connections
  • nslookup <domain> — DNS lookup

Linux / macOS

  • ifconfig or ip a — interface info
  • ping — connectivity
  • traceroute — route path
  • netstat -tulpn — listening ports
  • dig <domain> — DNS lookup

Troubleshooting (Quick Reference)

  1. Physical Layer
    • Check cables
    • Check link lights
    • Replace patch cable
  2. IP Layer
    • Check IP address
    • Check gateway
    • Ping local gateway
  3. DNS Layer
    • Test DNS resolution
    • Try alternate DNS
  4. Routing Layer
    • Check routing table
    • Trace route to destination
  5. Application Layer
    • Test service port
    • Check firewall rules
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Photo of EDK-Tech EDK-Tech3 days ago
0 10 1 minute read
Photo of EDK-Tech

EDK-Tech

I’m an emerging IT and electronics technician focused on building strong foundational skills in networking, connectivity, and hands‑on system troubleshooting. Alongside my IT and electronics work, I have experience in web development and WordPress engineering, including custom plugin development, shortcode systems, UI/UX improvements, and modular, scalable code design. I enjoy creating tools that solve real problems, improve workflows, and enhance the user experience.

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