CompTIA Network+ (N10-008) - Core Networking, Subnetting & Ports Flashcards

Question 1

Port Address Translation (PAT / NAT Overload)

Accepted Answer

• Function: Maps multiple private IPv4 addresses to a single public IPv4 address.
• Operation: Uses dynamic, unique source port numbers to differentiate sessions for each internal host.

Question 2

Wi-Fi 6 (802.11ax) Key Features

Accepted Answer

• Operating Frequency: **2.4 GHz, 5 GHz**, and **6 GHz** (Wi-Fi 6E).
• Key Multiplexing Feature: **OFDMA** (Orthogonal Frequency-Division Multiple Access), which divides channels into smaller sub-carriers to serve multiple clients simultaneously.

Question 3

SSH vs. Telnet Ports & Security

Accepted Answer

• `SSH` (Secure Shell): Port **22** (TCP) - Provides encrypted remote command-line administration.
• `Telnet`: Port **23** (TCP) - Transmits data in unencrypted plaintext (insecure).

Question 4

HTTP vs. HTTPS Protocols & Ports

Accepted Answer

• `HTTP`: Port **80** (TCP) - Unencrypted web traffic.
• `HTTPS`: Port **443** (TCP) - Encrypted web traffic using SSL/TLS.

Question 5

Domain Name System (DNS) Port & Function

Accepted Answer

• Port: **53** (UDP for standard queries, TCP for zone transfers)
• Function: Resolves human-readable FQDNs (e.g., `example.com`) to IP addresses.

Question 6

Remote Desktop Protocol (RDP) Port

Accepted Answer

• Port: **3389** (TCP/UDP)
• Function: Proprietary protocol developed by Microsoft to provide a user with a graphical interface to connect to another computer over a network.

Question 7

Dynamic Host Configuration Protocol (DHCP) Ports

Accepted Answer

• Server Port: **UDP 67**
• Client Port: **UDP 68**
• Function: Automatically assigns IP addresses, subnet masks, default gateways, and DNS server addresses to hosts.

Question 8

Email Protocols & Default Port Numbers

Accepted Answer

• `SMTP`: Port **25** (Plaintext), **587** (TLS submission) — Used to send mail.
• `POP3`: Port **110** (Plaintext), **995** (SSL/TLS) — Downloads and deletes mail from server.
• `IMAP`: Port **143** (Plaintext), **993** (SSL/TLS) — Syncs mail across client devices.

Question 9

Simple Network Management Protocol (SNMP) Ports

Accepted Answer

• `SNMP Queries`: **UDP 161**
• `SNMP Traps`: **UDP 162**
• Function: Used by network management systems to monitor and configure managed network devices via agents and MIBs.

Question 10

OSI Model 7 Layers (Top to Bottom)

Accepted Answer

7. **Application**: Network services to applications
6. **Presentation**: Data formatting, encryption, compression
5. **Session**: Session establishment and management
4. **Transport**: End-to-end connections (`TCP`/`UDP`)
3. **Network**: IP addressing and routing
2. **Data Link**: MAC addressing and physical framing
1. **Physical**: Binary transmission over physical media

*Mnemonic*: **A**ll **P**eople **S**eem **T**o **N**eed **D**ata **P**rocessing

Question 11

OSI Layer 2 vs. Layer 3 Devices & PDUs

Accepted Answer

• **Layer 2 (Data Link)**: Switches and Bridges. Process **Frames** using physical **MAC addresses**.
• **Layer 3 (Network)**: Routers and Layer 3 Switches. Process **Packets** using logical **IP addresses**.

Question 12

TCP vs. UDP Transport Protocols

Accepted Answer

• `TCP` (Transmission Control Protocol): Connection-oriented (uses 3-way handshake), reliable, guarantees delivery and order, higher overhead.
• `UDP` (User Datagram Protocol): Connectionless, unreliable (best-effort), lower overhead, ideal for real-time traffic (streaming, VoIP).

Question 13

IPv4 Usable Host Calculation Formula

Accepted Answer

To calculate usable host IP addresses in a CIDR subnet with prefix length $n$:

$$	ext{Usable Hosts} = 2^{(32 - n)} - 2$$

*Note*: Subtract 2 for the non-assignable **Network Address** (all host bits set to 0) and **Broadcast Address** (all host bits set to 1).

Question 14

/26 Subnet Calculation Example

Accepted Answer

For subnet mask `255.255.255.192` (/26):
• Host bits ($h$): $32 - 26 = 6$
• Total IPs: $2^6 = 64$
• Usable hosts: $64 - 2 = 62$
• Block size / Subnet increment: $256 - 192 = 64$

Question 15

Address Resolution Protocol (ARP)

Accepted Answer

• Function: Maps a known Layer 3 **IPv4 address** to an unknown Layer 2 **MAC address** on a local subnet.
• Request: Broadcast (`FF-FF-FF-FF-FF-FF`)
• Reply: Unicast

Question 16

IPv6 Address Properties & Link-Local Prefix

Accepted Answer

• Address Length: **128 bits** (written in hexadecimal, separated by colons).
• Link-Local Address Prefix: **`fe80::/10`**
• Every IPv6-enabled interface automatically self-assigns a link-local address for local communication without a DHCP server.

Question 17

Stateful vs. Stateless Firewalls

Accepted Answer

• **Stateless Firewall**: Filters traffic based on individual packet headers (IP, Port) using static rules (ACLs) without tracking connection state.
• **Stateful Firewall**: Tracks active TCP/UDP sessions in a connection table; automatically allows return traffic for legitimate established outbound requests.

Question 18

CompTIA 7-Step Troubleshooting Methodology

Accepted Answer

1. Identify the problem.
2. Establish a theory of probable cause.
3. Test the theory to determine cause.
4. Establish a plan of action to resolve the problem and implement the solution.
5. Verify full system functionality and, if applicable, implement preventive measures.
6. Document findings, actions, and outcomes.

Question 19

VLANs & 802.1Q Trunking Protocol

Accepted Answer

• **VLAN** (Virtual Local Area Network): Logically breaks up a switch into multiple broadcast domains at Layer 2.
• **IEEE 802.1Q**: The standard protocol for frame tagging across trunk links, adding a 4-byte VLAN tag into the Ethernet frame.

Question 20

File Transfer Protocols: FTP, SFTP, and FTPS

Accepted Answer

• `FTP`: Ports **20/21** (Plaintext data/control).
• `SFTP` (SSH File Transfer Protocol): Port **22** (Secure transfer using SSH).
• `FTPS` (FTP Secure): Ports **989/990** (FTP encapsulated inside SSL/TLS).

CompTIA Network+ (N10-008) - Core Networking, Subnetting & Ports

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