Skip to content

Instantly share code, notes, and snippets.

@timsonner

timsonner/network+.md

Created March 5, 2026 16:36
Show Gist options

  • Select an option

    Learn more about clone URLs
  • Save timsonner/1a03f74ce0812589c207dadd3b262e5e to your computer and use it in GitHub Desktop.

Select an option

Learn more about clone URLs
Save timsonner/1a03f74ce0812589c207dadd3b262e5e to your computer and use it in GitHub Desktop.
Download ZIP
Study sheet for Network+
Raw
network+.md

Network+ Study Sheet

Network+ Cable Standards

A consolidated reference for copper, fiber, and coax cable types, including speeds, distances, and optical standards (SX, LX, EX, ZX, SR, LR, ER, ZR).

Twisted‑Pair Copper (Ethernet)

Cable Type Max Speed Max Length Notes
Cat5 100 Mbps 100 m Legacy.
Cat5e 1 Gbps 100 m Most common baseline.
Cat6 1 Gbps (10 Gbps up to 55 m) 100 m Better shielding.
Cat6a 10 Gbps 100 m Enterprise standard.
Cat7 10 Gbps 100 m Shielded; not TIA‑standardized.
Cat8 25–40 Gbps 30 m Data centers; short‑run.

Copper Ethernet Standards (Base-T/TX)

Standard Max Speed Cable Type Max Length Notes
10BASE-T 10 Mbps Cat 3 or higher 100 m Legacy base Ethernet distance.
100BASE-TX 100 Mbps Cat 5 or higher 100 m Fast Ethernet. Uses 2 pairs.
1000BASE-T 1 Gbps Cat 5e or higher 100 m Gigabit Ethernet. Uses all 4 pairs.
10GBASE-T 10 Gbps Cat 6 (55 m) / 6a (100 m) 55m / 100m 10 Gigabit Ethernet over copper.
40GBASE-T 40 Gbps Cat 8 30 m Data center short connections.

Fiber Optic Standards (1G & 10G)

Gigabit Ethernet (1 Gbps)

Standard Meaning Wavelength Fiber Type Max Distance Notes
1000BASE‑SX Short 850 nm Multimode 220–550 m Short‑range LAN.
1000BASE‑LX Long 1310 nm Single‑mode (or MMF w/ mode conditioning) 5 km Common uplink.
1000BASE‑EX Extended 1310 nm Single‑mode ~40 km Metro fiber.
1000BASE‑ZX Extended Distance 1550 nm Single‑mode 70–80 km Long‑haul.

10‑Gigabit Ethernet (10 Gbps)

Standard Meaning Wavelength Fiber Type Max Distance Notes
10GBASE‑SR Short Range 850 nm Multimode 300–400 m Data centers.
10GBASE‑LR Long Range 1310 nm Single‑mode 10 km Enterprise WAN.
10GBASE‑ER Extended Range 1550 nm Single‑mode 40 km Carrier links.
10GBASE‑ZR Ultra‑Long Range 1550 nm Single‑mode 70–80 km Not IEEE‑standardized but widely used.

Multimode Fiber Categories (OM1–OM5)

Fiber Type Max Speed Max Distance Notes
OM1 1 Gbps 275 m Orange jacket.
OM2 1 Gbps 550 m Orange.
OM3 10 Gbps 300 m Aqua; laser‑optimized.
OM4 10 Gbps 400–500 m Aqua; higher performance.
OM5 40–100 Gbps 150 m Lime‑green; wideband.

Coaxial Cable Standards

Coax Type Max Speed Max Length Notes
RG‑6 1 Gbps+ (DOCSIS) Hundreds of meters Cable Internet/TV.
RG‑59 Lower speeds Short runs CCTV/analog video.
10BASE‑5 (Thicknet) 10 Mbps 500 m Vampire taps; legacy Ethernet.
10BASE‑2 (Thinnet) 10 Mbps 185 m BNC connectors; legacy Ethernet.

Quick Memory Tips (Cables)

  • Copper runs are 100 m, except Cat8 = 30 m.
  • Single‑mode = kilometers, multimode = hundreds of meters.
  • SX = short (850 nm), LX = long (1310 nm), ZX = longest (1550 nm).
  • 10G fiber: SR (short), LR (10 km), ER (40 km), ZR (70–80 km).
  • Thicknet/Thinnet: 500 m and 185 m.

Network+ Cisco IOS Commands

A quick reference guide for the essential Cisco IOS commands you may encounter on the CompTIA Network+ exam (PBQs and simulation labs).

1. Command Modes

Prompt Mode Description How to Enter
Router> User EXEC Basic viewing, limited commands. Default login mode.
Router# Privileged EXEC Full viewing, save/load configs. Type enable from User mode.
Router(config)# Global Configuration System-wide config changes. Type configure terminal from Privileged.
Router(config-if)# Interface Config Configure specific ports/interfaces. Type interface [name] from Global config.

2. Basic Navigation & Saving

  • enable (or en): Enter Privileged EXEC mode.
  • configure terminal (or conf t): Enter Global Configuration mode.
  • exit: Move back one mode level.
  • disable: Exit Privileged EXEC back to User EXEC.
  • copy running-config startup-config (or copy run start): Save current active configuration to NVRAM.
  • write memory (or wr): Older, faster way to save configuration.

3. Interface Configuration

  • interface [type] [number] (e.g., interface gigabitethernet 0/1 or int g0/1): Enter interface config mode.
  • ip address [IP] [Subnet Mask]: Assign an IPv4 address.
    • Example: ip address 192.168.1.1 255.255.255.0
  • ipv6 address [IPv6]/[Prefix]: Assign an IPv6 address.
  • no shutdown (or no shut): Enable/turn on the interface (ports are administratively down by default on routers).
  • description [text]: Add a description label to the port.

4. VLANs and Switchports

  • vlan [id] (e.g., vlan 10): Create or enter VLAN config mode.
  • name [name]: Name the VLAN (e.g., name Sales).
  • switchport mode access: Set the port to connect to an end device (workstation, printer).
  • switchport access vlan [id]: Assign the port to a specific VLAN.
  • switchport mode trunk: Set the port to be a trunk link (carries multiple VLANs between switches).
  • switchport trunk allowed vlan [id-list]: Restrict which VLANs can cross the trunk.

SVI (Switched Virtual Interface) & Inter-VLAN Routing

  • interface vlan [id] (e.g., int vlan 10): Create/enter the logical interface for a VLAN (SVI).
  • ip address [IP] [Subnet Mask]: Assign an IP address to the SVI (often acts as the default gateway for devices in that VLAN).
  • no shutdown: Enable the SVI.
  • ip routing: Enable IPv4 routing on a Layer 3 switch (run in Global Config mode).

5. Routing Protocols (RIP, EIGRP, OSPF)

RIP (Routing Information Protocol)

  • router rip: Enter RIP configuration mode.
  • version 2: Enable RIPv2 (supports VLSM/CIDR).
  • no auto-summary: Disable automatic classful summarization.
  • network [classful network address]: Advertise a network (e.g., network 192.168.1.0).

EIGRP (Enhanced Interior Gateway Routing Protocol)

  • router eigrp [AS-number]: Enter EIGRP configuration mode (e.g., router eigrp 100).
  • network [network address] [wildcard mask]: Advertise a network (e.g., network 10.0.0.0 0.0.0.255).
  • no auto-summary: Disable automatic summarization (often needed in modern networks).

OSPF (Open Shortest Path First)

  • router ospf [process-ID]: Enter OSPF configuration mode (e.g., router ospf 1).
  • network [network address] [wildcard mask] area [area-id]: Advertise a network into a specific area (e.g., network 192.168.1.0 0.0.0.255 area 0).
  • router-id [IP]: Manually set the OSPF router ID for stability.

6. Verification & Troubleshooting (show commands)

Tip: Run these from Privileged EXEC mode (#). To run them from Global Config mode, put do in front (e.g., do show run).

  • show running-config (or sh run): Displays the current, active configuration.
  • show ip interface brief (or sh ip int br): Extremely useful. Shows all interfaces, their IP addresses, and up/down status.
  • show interfaces: Detailed statistics, errors, and MAC/hardware info for interfaces.
  • show mac address-table: Displays the switch's MAC address table (learned MACs mapped to ports).
  • show vlan (or sh vlan brief): Lists all configured VLANs and assigned ports.
  • show ip route: Displays the router's routing table (learned and connected networks).
  • ping [IP]: Test basic connectivity (ICMP echo).
  • traceroute [IP]: Trace the path to a destination.

Quick Memory Tips (IOS Commands)

  • Always remember to run no shut after configuring an IP address on a router interface!
  • show ip int brief is your best friend for verifying interface statuses on the PBQs.
  • If you get stuck in a command output or ping loop, try Ctrl + Shift + 6 to abort.
  • Use ? if you forget a command syntax in a simulation lab.

Network+ Routing Protocols

A consolidated reference for dynamic routing protocols, their algorithms, metrics, and administrative distances for the CompTIA Network+ exam.

1. Routing Categories

  • IGP (Interior Gateway Protocol): Routes traffic within a single Autonomous System (AS). Examples: OSPF, RIP, EIGRP, IS-IS.
  • EGP (Exterior Gateway Protocol): Routes traffic between different Autonomous Systems (the Internet). Example: BGP.

Routing Types

  • Distance-Vector: Routers share their entire routing table with immediate neighbors. They determine the best path based on distance (like hops). Examples: RIP, EIGRP.
  • Link-State: Routers maintain a complete map/topology of the network. They only send updates when a change occurs. Calculates the best path based on link cost. Examples: OSPF, IS-IS.
  • Path-Vector: Maintains path information and avoids routing loops by tracking AS paths. Example: BGP.

2. Dynamic Routing Protocols at a Glance

Protocol Category IGP / EGP Algorithm Metric (How it calculates routes)
RIPv2 Distance-Vector IGP Bellman-Ford Hop Count (Max 15 hops, 16 is unreachable).
OSPF Link-State IGP Dijkstra Shortest Path First (SPF) Cost (Based on link bandwidth; faster link = lower cost).
IS-IS Link-State IGP Dijkstra Shortest Path First (SPF) Cost (Assigned by admin or based on bandwidth).
EIGRP Advanced Distance-Vector (Hybrid) IGP DUAL (Diffusing Update Algorithm) Bandwidth & Delay (Load and Reliability optionally). Cisco proprietary (now open but mostly Cisco).
BGP Path-Vector EGP Best Path Selection Algorithm Path Attributes (AS-Path, Next hop, Local Pref, MED). The routing protocol of the Internet.

3. Route Calculation Details

OSPF (Open Shortest Path First)

  • Builds a complete topology tree of the network.
  • Uses Link-State Advertisements (LSAs) to inform neighbors of link changes.
  • Metric = Cost: Calculated as Reference Bandwidth / Interface Bandwidth. High bandwidth links (like 1Gbps Fiber) have a lower cost than low bandwidth links (like T1 lines).
  • Divides networks into Areas (Area 0 is the backbone area).

RIP (Routing Information Protocol)

  • Very basic, older protocol.
  • Metric = Hop Count: The number of routers a packet must pass through.
  • It does not factor in link speed. A 10Gbps link with 2 hops is considered "worse" than a 10Mbps link with 1 hop.
  • Sends full routing tables every 30 seconds (creates network overhead).

BGP (Border Gateway Protocol)

  • Moves traffic between ISPs and large enterprise networks using Autonomous System Numbers (ASNs).
  • Rather than standard metrics, it uses complex policy rules and Path Attributes.
  • It looks at the shortest AS Path (fewest autonomous systems crossed) as a primary metric.

EIGRP (Enhanced Interior Gateway Routing Protocol)

  • Keeps backup routes readily available for instant convergence if the primary fails (Successor and Feasible Successor).
  • Metric is a complex formula that defaults to evaluating the slowest Bandwidth along the path plus the cumulative Delay.

4. Administrative Distance (AD)

Administrative Distance determines the "trustworthiness" or preference of a route source. If a router learns about the same destination from two different protocols, it will choose the one with the lowest Administrative Distance.

Route Source Default AD Notes
Directly Connected 0 Always preferred over anything else.
Static Route 1 Manually configured by an admin.
eBGP 20 External BGP routes.
EIGRP 90 Highly trusted IGP.
OSPF 110 Standard interior routing.
IS-IS 115 Slightly less trusted than OSPF by default on Cisco.
RIP 120 Least trusted dynamic protocol.

Quick Memory Tips (Routing)

  • IGP vs EGP: Everything is IGP except BGP. BGP runs the Internet.
  • OSPF = Cost/Bandwidth (Link-State). Divides into Areas.
  • RIP = Hop Count (Distance-Vector). Max 15 hops.
  • EIGRP = Bandwidth + Delay (Hybrid). Cisco environments.
  • Lowest AD wins! Connected (0) > Static (1) > OSPF (110) > RIP (120).

802.11 Wireless Standards

This table summarizes the key characteristics of major Wi‑Fi standards for the CompTIA Network+ exam, including frequency bands, maximum speeds, channel widths, and notable features.

Quick Reference Table

Standard Frequency Max Speed Channel Width Key Features
802.11a 5 GHz 54 Mbps 20 MHz OFDM
802.11b 2.4 GHz 11 Mbps 22 MHz DSSS
802.11g 2.4 GHz 54 Mbps 20 MHz OFDM
802.11n 2.4 / 5 GHz 600 Mbps 20 / 40 MHz MIMO, HT (High Throughput)
802.11ac 5 GHz ~3.5 Gbps 20 / 40 / 80 / 160 MHz MU‑MIMO, VHT (Very High Throughput)
802.11ax 2.4 / 5 / 6 GHz ~9.6 Gbps Flexible (OFDMA-based) MU‑MIMO, OFDMA, HE (High Efficiency)

Notes for Network+ Exam

  • MIMO introduced in 802.11n
  • MU‑MIMO introduced in 802.11ac (downlink only)
  • Full uplink/downlink MU‑MIMO in 802.11ax
  • Channel bonding grows with each generation (40 MHz → 80 MHz → 160 MHz)
  • OFDMA is unique to 802.11ax
  • Wi‑Fi Generations:
    • Wi‑Fi 4 = 802.11n
    • Wi‑Fi 5 = 802.11ac
    • Wi‑Fi 6/6E = 802.11ax

2.4 GHz Channels & Frequencies

The 2.4 GHz band primarily uses channels 1-11 in North America. Each channel is spaced 5 MHz apart. For the Network+ exam, it's crucial to know the three non-overlapping channels:

Channel Center Frequency Notes
1 2412 MHz Non-overlapping
2 2417 MHz
3 2422 MHz
4 2427 MHz
5 2432 MHz
6 2437 MHz Non-overlapping
7 2442 MHz
8 2447 MHz
9 2452 MHz
10 2457 MHz
11 2462 MHz Non-overlapping
12 2467 MHz Available outside NA
13 2472 MHz Available outside NA
14 2484 MHz Japan only

Classful Subnets & RFC 1918

Classful Subnets (IPv4)

Before CIDR (Classless Inter-Domain Routing), IP addresses were divided into predefined classes based on their leading bits:

  • Class A
    • Range: 1.0.0.0 – 126.255.255.255
    • Default Subnet Mask: 255.0.0.0 (/8)
  • Class B
    • Range: 128.0.0.0 – 191.255.255.255
    • Default Subnet Mask: 255.255.0.0 (/16)
  • Class C
    • Range: 192.0.0.0 – 223.255.255.255
    • Default Subnet Mask: 255.255.255.0 (/24)
  • Class D (Multicast)
    • Range: 224.0.0.0 – 239.255.255.255
  • Class E (Experimental)
    • Range: 240.0.0.0 – 254.255.255.255

(Note: 127.0.0.0/8 is reserved for loopback addresses)

RFC 1918 (Private IP Addresses)

RFC 1918 defines IP addresses that are meant for internal networks (LANs). They are non-routable on the public internet, so routers will silently drop packets destined for these addresses from crossing out to the internet.

  • Class A Private Range
    • 10.0.0.0 to 10.255.255.255
  • Class B Private Range
    • 172.16.0.0 to 172.31.255.255
  • Class C Private Range
    • 192.168.0.0 to 192.168.255.255
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment