CompTIA Network+ (N10-008) - Protocols & Subnetting Flashcards

Question 1

DNS (Domain Name System)

Accepted Answer

Port: `53` (Uses `UDP` for standard queries and `TCP` for zone transfers or responses exceeding 512 bytes).
Resolves human-readable domain names (e.g., `example.com`) into IP addresses.

Question 2

DHCP (Dynamic Host Configuration Protocol)

Accepted Answer

Ports: `67` (Server) and `68` (Client) over `UDP`.
Automatically assigns IP addresses, subnet masks, default gateways, and DNS server addresses to network clients.

Question 3

HTTPS (Hypertext Transfer Protocol Secure)

Accepted Answer

Port: `443` over `TCP`.
Provides encrypted web communication using TLS/SSL to secure data transmission between web browsers and servers.

Question 4

SSH (Secure Shell)

Accepted Answer

Port: `22` over `TCP`.
Provides encrypted command-line remote access, secure administrative login, and encrypted file transfers (`SFTP`).

Question 5

Usable Host Calculation Formula

Accepted Answer

The formula to calculate the number of usable host IP addresses in a subnet is:
$$	ext{Usable Hosts} = 2^h - 2$$
Where $h$ is the number of host bits remaining ($32 - 	ext{CIDR prefix}$). Subtract $2$ for the network and broadcast addresses.

Question 6

IPv4 Subnetting: /24 CIDR

Accepted Answer

- Subnet Mask: `255.255.255.0`
- Host Bits ($h$): 8
- Total IPs: $2^8 = 256$
- Usable Hosts: $2^8 - 2 = 254$

Question 7

IPv4 Subnetting: /25 CIDR

Accepted Answer

- Subnet Mask: `255.255.255.128`
- Host Bits ($h$): 7
- Total IPs: $2^7 = 128$
- Usable Hosts: $2^7 - 2 = 126$

Question 8

IPv4 Subnetting: /26 CIDR

Accepted Answer

- Subnet Mask: `255.255.255.192`
- Host Bits ($h$): 6
- Total IPs: $2^6 = 64$
- Usable Hosts: $2^6 - 2 = 62$

Question 9

IPv4 Subnetting: /27 CIDR

Accepted Answer

- Subnet Mask: `255.255.255.224`
- Host Bits ($h$): 5
- Total IPs: $2^5 = 32$
- Usable Hosts: $2^5 - 2 = 30$

Question 10

IPv4 Subnetting: /28 CIDR

Accepted Answer

- Subnet Mask: `255.255.255.240`
- Host Bits ($h$): 4
- Total IPs: $2^4 = 16$
- Usable Hosts: $2^4 - 2 = 14$

Question 11

IPv4 Subnetting: /29 CIDR

Accepted Answer

- Subnet Mask: `255.255.255.248`
- Host Bits ($h$): 3
- Total IPs: $2^3 = 8$
- Usable Hosts: $2^3 - 2 = 6$

Question 12

IPv4 Subnetting: /30 CIDR

Accepted Answer

- Subnet Mask: `255.255.255.252`
- Host Bits ($h$): 2
- Total IPs: $2^2 = 4$
- Usable Hosts: $2^2 - 2 = 2$
- Primary Use: Point-to-point serial and router links.

Question 13

OSI Model Layers (1–7)

Accepted Answer

1. **Physical**: Cables, bits, hubs
2. **Data Link**: MAC addresses, frames, switches
3. **Network**: IP addresses, packets, routers
4. **Transport**: TCP/UDP, segments, ports
5. **Session**: Dialog control, sessions
6. **Presentation**: Encryption, data formatting
7. **Application**: Network applications (HTTP, DNS)

Question 14

TCP vs. UDP

Accepted Answer

- **TCP (Transmission Control Protocol)**: Connection-oriented, reliable, guarantees packet delivery and ordering via a 3-way handshake (`SYN`, `SYN-ACK`, `ACK`).
- **UDP (User Datagram Protocol)**: Connectionless, best-effort delivery, low latency, no error recovery. Ideal for real-time services like streaming and VoIP.

Question 15

802.11ac (Wi-Fi 5) Wireless Standard

Accepted Answer

- Band: Exclusively **5 GHz**
- Max Speed: Multi-Gbps (up to ~6.9 Gbps)
- Key Features: Downlink MU-MIMO, beamforming, and wider channel bonding up to 160 MHz.

Question 16

802.11ax (Wi-Fi 6) Wireless Standard

Accepted Answer

- Bands: **2.4 GHz** and **5 GHz** (plus **6 GHz** with Wi-Fi 6E)
- Key Features: **OFDMA** (Orthogonal Frequency-Division Multiple Access), bi-directional MU-MIMO, and Target Wake Time (TWT) for improved battery life.

Question 17

OSPF (Open Shortest Path First)

Accepted Answer

- Type: **Interior Gateway Protocol (IGP)**
- Algorithm: **Link-State** (Dijkstra's SPF)
- Metric: Cost (calculated based on bandwidth)
- Features: Fast convergence, hierarchical structure using Area `0` (backbone).

Question 18

BGP (Border Gateway Protocol)

Accepted Answer

- Type: **Exterior Gateway Protocol (EGP)**
- Algorithm: **Path-Vector**
- Purpose: Routes traffic between different Autonomous Systems (AS) across the internet using policy-based routing decisions.

Question 19

IEEE 802.1Q (VLAN Tagging)

Accepted Answer

The networking standard for supporting Virtual Local Area Networks (VLANs) on an Ethernet network. It inserts a **4-byte tag** into the Ethernet frame header to identify the VLAN ID (VID).

Question 20

Access Port vs. Trunk Port

Accepted Answer

- **Access Port**: Belongs to a single VLAN; carries untagged traffic; typically connects end-user devices (PCs, printers).
- **Trunk Port**: Carries traffic for multiple VLANs simultaneously; tags frames using `802.1Q`; connects switches, routers, or hypervisors.

CompTIA Network+ (N10-008) - Protocols & Subnetting

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