1. What is the key functional difference between a Collision Domain and a Broadcast Domain?
- Collision domain — a network segment where two devices transmitting at the same time collide. On a hub (shared medium), all ports are one collision domain.
- Broadcast domain — the boundary within which a broadcast frame reaches every device. Broadcasts stop at routers (or VLAN boundaries).
NETWORK DOMAINS
Collision Domain Broadcast Domain
───────────────── ────────────────
[PC-A] [PC-A]
│ │
[ HUB ] ← all ports [ Switch ]
│ │ │ │ │ │
[PC] [PC] [PC] [PC][PC][PC]
│ │ │
└──┴──┴──→
ONE collision domain ONE broadcast domain
Switch:
┌───────────────────────────────┐
│ SWITCH │
│ │
│ Port 1 → PC-A = Collision 1 │
│ Port 2 → PC-B = Collision 2 │
│ Port 3 → PC-C = Collision 3 │
└───────────────────────────────┘
│
└── One Broadcast DomainKey takeaway:
Switch → breaks Collision Domains
Router → breaks Broadcast Domains
VLAN → creates separate Broadcast Domains2. Which of the following accurately describes the differences between a MAC address and an IP address?
- MAC address — a 48-bit hardware address associated with the network interface. Operates at Layer 2.
- IP address — a logical address assigned by software/network configuration. Operates at Layer 3 and can change depending on the network.
DEVICE
│
┌─────────┴─────────┐
│ │
MAC Address IP Address
Layer 2 Layer 3
│ │
"Who are you?" "Where are you?"
│ │
AA:BB:CC:DD:EE:FF 192.168.1.20| MAC | IP | |
|---|---|---|
| Size | 48-bit | 32-bit (IPv4) / 128-bit (IPv6) |
| Layer | 2 (Data Link) | 3 (Network) |
| Purpose | Device/interface identification | Logical addressing & routing |
| Changes | Usually stable | Can change |
| Example | AA:BB:CC:DD:EE:FF | 192.168.1.20 |
Think:
MAC = your identity on the local network
IP = your current network address3. How does a Gateway differ fundamentally from a standard Router?
- Router — connects networks using the same networking protocol, primarily forwarding IP packets between networks.
- Gateway — acts as an entry/exit point and, in the broader sense, can translate between different protocols, systems, or architectures.
Router
────────────────────────────────────
Network A Network B
192.168.1.0 10.0.0.0
│ │
│ [ ROUTER ] │
└───────────┬───────────┘
│
IP → IP forwarding
Gateway
────────────────────────────────────
IP Network
│
▼
┌───────────┐
│ GATEWAY │
│ Translator│
└─────┬─────┘
│
▼
Different / Legacy SystemEasy way to remember:
Router = forwards traffic
Gateway = connects/possibly translates between different systems4. What is the operational purpose of a Brouter (Bridging Router)?
A brouter is a hybrid device that combines the behavior of a bridge (Layer 2) and a router (Layer 3).
┌──────────────┐
Incoming Traffic │ BROUTER │
────────────────►│ │
└──────┬───────┘
│
┌──────────┴──────────┐
│ │
Routable Non-routable
traffic traffic
│ │
▼ ▼
ROUTE by IP BRIDGE by MAC
Layer 3 Layer 2So:
IP traffic → Router behavior → Layer 3
Legacy traffic → Bridge behavior → Layer 2It is useful in networks carrying a mixture of routable and legacy/non-routable traffic.
5. In network architecture terminology, what are Nodes and Links?
- Node — any device that participates in network communication.
- Link — the communication path connecting two nodes.
Link
────────────────
│ │
▼ ▼
[Node A] [Node B]
PC RouterA more complex network:
[Router]
/ \
/ \
[Switch] [Server]
/ \
/ \
[PC-A] [PC-B]
Nodes = PC-A, PC-B, Switch, Router, Server
Links = cables / fiber / wireless connectionsRemember:
Node = endpoint/device
Link = path between devices6. How does the Address Resolution Protocol (ARP) function on a local network?
ARP resolves a known IP address into the corresponding MAC address on a local network.
The problem:
Application knows:
IP = 192.168.1.50
But Ethernet needs:
MAC = ??ARP solves this:
PC-A
IP: 192.168.1.10
MAC: AA:AA:AA
│
│ ARP Request (Broadcast)
│ "Who has 192.168.1.50?"
▼
┌──────────────────────────────────┐
│ LOCAL NETWORK │
│ │
│ PC-B PC-C PC-D │
│ │ │ │ │
│ └───────────┴───────────┘ │
│ │
│ PC-B owns 192.168.1.50 │
└──────────────────────────────────┘
│
│ ARP Reply (Unicast)
│ "192.168.1.50 = BB:BB:BB"
▼
PC-A stores mapping in ARP cacheThe flow is:
Known IP
↓
ARP Request (Broadcast)
↓
Owner of IP responds
↓
ARP Reply
↓
IP → MAC mapping cached
↓
Ethernet frame can be sentARP works within the local network. Routers do not forward ARP broadcasts across networks.
7. What is the correct structural sequence for the 4-step DHCP lease process?
The DHCP process is remembered as DORA:
D → Discover
O → Offer
R → Request
A → AcknowledgeFull sequence:
DHCP SERVER
│
│
Client │
│ │
│── DISCOVER ────►│
│ "Any DHCP │
│ server?" │
│ │
│◄──── OFFER ─────│
│ "Use this IP" │
│ │
│── REQUEST ─────►│
│ "I want it" │
│ │
│◄──── ACK ───────│
│ "Approved!" │
│ │
▼
IP lease activeDORA =
Discover → Offer → Request → Acknowledge8. What catastrophic network event does Spanning Tree Protocol (STP) prevent by blocking redundant switch ports?
STP prevents Layer 2 switching loops, which can cause broadcast storms.
Without STP:
┌───────────┐
│ Switch A │
└─────┬─────┘
/ \
/ \
▼ ▼
┌────────┐ ┌────────┐
│Switch B│ │Switch C│
└────┬───┘ └───┬────┘
\ /
\ /
└─────┘
▲
│
LOOPA broadcast could circulate:
Broadcast
↓
Switch A
↓
Switch B
↓
Switch C
↓
Switch A
↓
Switch B
↓
...
↓
ENDLESS LOOPSTP blocks one redundant path:
Switch A
/ \
/ \
▼ ▼
Switch B Switch C
\ /
\ /
──X────
BLOCKED
No active Layer 2 loopIf the active path fails, STP can activate the backup path.
Remember:
STP = prevents switching loops
↓
Prevents broadcast storms9. What is the primary network efficiency benefit of Piggybacking?
Piggybacking puts an ACK together with an outgoing data frame instead of sending a separate ACK.
Without piggybacking:
A B
│ │
│────── DATA ─────────────────►│
│ │
│◄───── ACK ───────────────────│
│ │
│────── DATA ─────────────────►│
│ │With piggybacking:
A B
│ │
│────── DATA ─────────────────►│
│ │
│◄──── DATA + ACK ─────────────│
│ │One frame does two jobs:
Normal:
DATA + ACK
↓ ↓
2 frames
Piggybacking:
DATA + ACK
↓
1 frameBenefit:
Fewer frames
↓
Less overhead
↓
Better bandwidth efficiency10. Which communication mode allows simultaneous bidirectional data transmission between two endpoints?
The answer is Full-Duplex.
Simplex
────────────────
A ─────────────► B
Only one direction
Half-Duplex
────────────────
A ─────────────► B
A ◄───────────── B
Both directions,
but NOT at the same time
Full-Duplex
────────────────
A ─────────────► B
A ◄───────────── B
Both directions
AT THE SAME TIMEExamples:
Simplex → Keyboard → Computer
Half-Duplex → Walkie-talkie
Full-Duplex → Telephone call11. What is a Virtual Local Area Network (VLAN), and what are its primary administrative benefits?
A VLAN logically divides one physical switch into multiple isolated networks.
Without VLANs:
Physical Switch
┌──────────────────────┐
│ PC PC PC PC PC PC │
│ Everyone together │
└──────────────────────┘With VLANs:
ONE PHYSICAL SWITCH
┌──────────────────────────┐
│ │
│ VLAN 10 → SALES │
│ [PC][PC][PC][PC] │
│ │
│ VLAN 20 → IT │
│ [PC][PC][PC][PC] │
│ │
│ VLAN 30 → HR │
│ [PC][PC][PC][PC] │
│ │
└──────────────────────────┘Think of it as:
1 physical switch
↓
┌──────┼──────┐
↓ ↓ ↓
VLAN10 VLAN20 VLAN30
Sales IT HRBenefits:
VLAN
│
├── Security
│ ↓
│ Departments isolated
│
├── Less broadcast traffic
│ ↓
│ Broadcast stays inside VLAN
│
└── Flexibility
↓
Logical grouping without
changing physical cables12. What are the three core principles defined by the CIA Triad in network security?
The CIA Triad consists of:
CIA TRIAD
│
┌─────────┼─────────┐
│ │ │
▼ ▼ ▼
Confidentiality Integrity Availability
│ │ │
▼ ▼ ▼
Keep it Keep it Keep it
secret correct reachableConfidentiality
Only authorized people
↓
can read the data
Example:
Encryption + Access ControlIntegrity
Data should not be
changed illegally
Example:
Hashing + Digital SignaturesAvailability
System should be
accessible when needed
Example:
Backups + RedundancyEasy memory trick:
C = Confidential → Secret
I = Integrity → Correct
A = Availability → Accessible13. What is the operational difference between Symmetric and Asymmetric Encryption?
Symmetric encryption uses one shared key:
SAME KEY
│
▼
Plaintext ──► [🔑] ──► Ciphertext
│
▼
[🔑]
│
▼
PlaintextThe same key is used for encryption and decryption.
Asymmetric encryption uses a key pair:
KEY PAIR
│
┌─────────┴─────────┐
▼ ▼
Public Key Private Key
│ │
│ Encrypt │ Decrypt
▼ ▼
Plaintext ─────────► CiphertextComparison:
SYMMETRIC ASYMMETRIC
────────── ──────────
Keys One shared key Public + Private
Speed FAST SLOWER
Key sharing Difficult Easier
Examples AES RSA, ECCReal-world systems commonly combine them:
Asymmetric encryption
↓
Securely establish/exchange a key
↓
Symmetric encryption
↓
Encrypt large amounts of data efficiently14. What is the main difference between TCP and UDP protocols?
TCP is connection-oriented and reliable.
UDP is connectionless and best-effort.
TCP
────────────────────────────────
Client Server
│ │
│──── SYN ────────────────────►│
│◄─── SYN-ACK ────────────────│
│──── ACK ────────────────────►│
│ │
│════ Reliable Data ═════════►│
│◄════ ACK / Retransmission ══│
│ │
UDP
────────────────────────────────
Client Server
│ │
│──── DATA ──────────────────►│
│──── DATA ──────────────────►│
│──── DATA ────────────────X │
│ │
│ No handshake │
│ No ACK │
│ No retransmission │| TCP | UDP | |
|---|---|---|
| Connection | Yes | No |
| Reliability | Reliable | Best-effort |
| Ordering | Yes | No guarantee |
| Retransmission | Yes | No |
| Overhead | Higher | Lower |
| Typical uses | Web, email, file transfer | Gaming, VoIP, streaming, DNS |
Easy memory:
TCP = Trust / Correctness
UDP = Urgency / Speed15. What happens when a user enters a website address (URL) in a browser?
The browser goes through several steps:
User enters:
https://example.com
│
▼
┌─────────────┐
│ DNS Lookup │
└──────┬──────┘
│
▼
IP Address
93.184.216.34
│
▼
┌─────────────┐
│ TCP Handshake│
└──────┬──────┘
│
▼
┌─────────────┐
│ TLS Handshake│
│ (HTTPS) │
└──────┬──────┘
│
▼
HTTP Request
GET /
│
▼
Server
│
▼
HTTP Response
│
▼
Browser renders
the pageStep by step:
1. URL entered
↓
2. DNS finds the IP address
↓
3. TCP connection established
↓
4. TLS encryption established
(for HTTPS)
↓
5. Browser sends HTTP request
↓
6. Server sends response
↓
7. Browser renders the webpagePremium Content
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