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Exercises
I. FILL IN THE BLANKS
1. The hostname command is used to display _____________.
2. The length of a IPv4 and a IPv6 is ____________ and ___________
bytes respectively.
3. An access point is used to connect _________.
4. The ping command is used to _________.
5. HTTPS transfer ___________ data.
Answer:
1.
The hostname command
is used to display the name of the computer (host) on the network.
2.
The length of an IPv4 and
an IPv6 is 4 and 16 bytes
respectively.
1.
Note:
In bits, these are 32 bits and 128 bits respectively.
An access
point is used to connect wireless devices to a wired network.
The ping command
is used to test or verify network connectivity between two devices.
HTTPS transfers encrypted data.
II. MULTIPLE CHOICE QUESTIONS:
1. Which device is required to connect multiple heterogeneous
networks?
A) Hub
B) Switch
C) Router
D) Access Point
Answer:
The correct option is
✅ C) Router.
Explanation
A router is
a Layer 3 (Network Layer) device specifically designed to connect multiple
different or heterogeneous networks. Unlike other networking
hardware, routers use logical IP addresses to determine the
most efficient path for data packets to travel between distinct network segments.
They are capable of translating protocols and managing traffic between diverse
architectures, such as linking a Local Area Network (LAN) to a Wide Area
Network (WAN) or the Internet.
Why other options are incorrect
·
❌ A) Hub:
A hub is a simple Layer 1 (Physical Layer) device that broadcasts data to all
connected devices within a single network segment. It cannot
distinguish between different networks or manage traffic intelligently.
·
❌ B) Switch:
A switch primarily operates at Layer 2 (Data Link Layer) and connects multiple
devices within the same network (LAN). While it uses MAC
addresses to forward data to specific recipients, it does not typically connect
heterogeneous networks.
·
❌ D) Access
Point: An Access Point (AP) acts as a bridge between wired and
wireless segments of the same local network. Its primary purpose is to
provide wireless connectivity to devices rather than routing data between
multiple different networks.
2. Which is the largest type of computer network?
A) PAN
B) LAN
C) MAN
D) WAN
Answer:
The correct option is
✅ D) WAN.
Explanation
A WAN (Wide
Area Network) is the largest type of computer network because it spans
vast geographical distances, such as cities, countries, continents, or even the
entire globe. It typically connects multiple smaller networks like LANs and
MANs using technologies such as leased lines, fiber optics, and satellites.
The Internet is the most prominent and largest example of a
WAN.
3. Which protocol transfers encrypted data instead of plain data?
A) HTTP
B) HTTPS
C) FTP
D) SMTP
Answer:
The correct answer is
✅ B) HTTPS.
Explanation
HTTPS (Hypertext Transfer Protocol Secure) is
the secure version of HTTP. It uses encryption protocols such as SSL (Secure
Sockets Layer) or TLS (Transport Layer Security) to encrypt
data exchanged between a web browser and a server. This ensures that sensitive
information, such as passwords and credit card details, is unreadable if
intercepted by unauthorized parties.
Why other options are incorrect
·
❌ A) HTTP:
This is a standard protocol for transferring web data but transmits information
in plain text. Because it lacks encryption, any data sent over HTTP
can be easily intercepted and read by attackers.
·
❌ C) FTP:
File Transfer Protocol is designed for moving files between systems but does
not provide encryption by default. Usernames, passwords, and file contents are
sent in plain text unless a secure variant like SFTP or FTPS
is used.
·
❌ D) SMTP:
Simple Mail Transfer Protocol is used for sending emails. Like HTTP and FTP,
the original SMTP specification does not inherently encrypt data; messages are
sent in plain text unless security extensions like SMTPS or
STARTTLS are applied.
4. How many bytes are
reserved for OUI in a MAC address?
A) 3 B) 8 C) 24 D) 12
Answer:
The correct option is
✅ A) 3.
Explanation
In a standard 48-bit
MAC address (also known as EUI-48), the OUI (Organizationally
Unique Identifier) consists of the first 3 bytes (or 24
bits).
·
OUI
(3 bytes): Identifies the
manufacturer or vendor of the network interface card (NIC) and is assigned by
the IEEE.
·
NIC-Specific
(3 bytes): The remaining 3
bytes are used by the manufacturer to uniquely identify the specific device.
·
Total
Length: Since a full MAC
address is 6 bytes (48 bits), the OUI makes up exactly half of the
address.
Why other options are incorrect
·
❌ B) 8: A
standard MAC address is only 6 bytes long in total. 8 bytes refers to the total
length of an EUI-64 address, not the OUI portion.
·
❌ C) 24: While
there are 24 bits in an OUI, the question asks for the number
of bytes. There are 8 bits in 1 byte, so 24 bits equals 3 bytes.
·
❌ D) 12: A
MAC address is represented by 12 hexadecimal digits, but these 12
digits represent only 6 bytes total.
5. IP address can be
automatically assigned if the network is connected with
A) Access Point
B) Mail Server
C) Web Server
D) DHCP Server
Answer:
The correct option is
✅ D) DHCP Server.
Explanation
An IP address is
automatically assigned to devices in a network through a protocol called Dynamic
Host Configuration Protocol (DHCP). When a device (the DHCP client)
connects to a network, it broadcasts a request for configuration details.
A DHCP Server listens for this request and automatically
provides a unique IP address from a pre-defined pool, along with other essential
settings like the subnet mask, default gateway, and DNS server addresses.
Why other options are incorrect
·
❌ A) Access
Point: While many modern consumer routers combine an Access Point with
a DHCP server, a standalone Access Point’s primary job is to provide wireless
connectivity to a wired network. It does not inherently handle IP address
assignment unless it has a built-in DHCP service.
·
❌ B) Mail
Server: This server is specialized for handling email services
(sending/receiving mail using protocols like SMTP, POP, or IMAP). It does not
manage network configurations or assign IP addresses.
·
❌ C) Web
Server: A Web Server hosts websites and serves content to
users via HTTP/HTTPS. It is an end destination on a network rather than a
service that manages the network's internal addressing.
III. SHORT ANSWER QUESTIONS
1. Mention the name of components required to set up a MAN
network. Draw a block
diagram of a MAN network labeling name of each component.
(Hint: MAN
network is a connection of multiple LAN)
Answer:
A MAN network connects
multiple LANs using Routers, Switches, and high-speed Fiber Optic Cables, forming a central backbone with distribution
layers for various campuses/buildings, requiring Access Points for wireless, Firewalls for security, and an ISP Gateway for internet access, all managed by Network Servers and monitored by management tools. The
block diagram shows individual LANs connecting via routers to a core switch
(backbone), which links to other LANs and the internet gateway.
Key Components of a MAN Network
1.
Multiple
LANs: The foundational
elements, representing individual campus or building networks.
2.
Routers: Connect
different LANs and direct traffic between them, often at the edge of the MAN.
3.
Switches (Core & Distribution): High-capacity switches form the MAN
backbone, while distribution switches connect to end-user devices.
4.
Transmission
Media: Primarily Fiber Optic Cables for high-speed backbone, plus Microwave
Links or leased lines.
5.
Wireless
Access Points (APs): For wireless
device connectivity.
6.
Network
Servers: For services
like DHCP, DNS.
7.
Firewalls/Security
Devices: Protect the
network from unauthorized access.
8.
ISP/Internet
Gateway: Connects the
entire MAN to the wider internet.
2. Why hostname
should not be used to identify a computer in a computer network?
Answer:
Hostnames shouldn't be
the sole identifier in networks because they're not guaranteed unique, can
change easily, and only identify a device locally, failing in complex
routing; instead, stable, globally unique IP addresses (or FQDNs) provide
reliable, routable identification for devices across different networks,
ensuring correct communication.
Key reasons hostnames
are unreliable:
·
Lack
of Uniqueness:
Multiple devices can
accidentally have the same hostname, causing conflicts, or a single device
might have several (e.g., for different services).
·
Volatility:
Hostnames (like MyLaptop or Server01) are user-friendly
labels that can be changed by anyone, making them inconsistent
identifiers.
·
Local
Scope:
A hostname usually
only works within its local network (LAN) or domain; it doesn't inherently
tell routers how to find that device across the internet.
·
Security
Risks:
Predictable hostnames
can reveal server roles (e.g., mailserver1), making them easier targets for
attackers.
Why IP addresses (or
FQDNs) are better:
·
Unique
& Stable:
Each device gets a
unique IP address (e.g., 192.168.1.100) or a Fully Qualified Domain Name (FQDN,
e.g., mail.example.com), which are more permanent identifiers.
·
Routable:
IP addresses are the
fundamental addresses used by routers to send data packets across the
globe.
·
DNS
Resolution:
The Domain Name System
(DNS) translates human-readable hostnames (or FQDNs) into these numerical IP
addresses, allowing both convenient naming and reliable routing.
In short, hostnames
are for human convenience, while IP addresses are for network
functionality; using IPs (or FQDNs) provides stability, uniqueness, and
proper routing essential for modern networks.
3. Give five examples
of valid and five examples of invalid IPv4 addresses.
(Hint: Each
segment of an IPv4 address has a fixed length)
Answer:
Valid IPv4 addresses
have four segments (octets) of numbers (0-255) separated by dots, while invalid
ones violate these rules, such as having numbers over 255, missing segments,
extra segments, non-numeric characters, or negative numbers, like 192.168.1.1 (valid)
vs. 256.0.0.1 (invalid).
Five Valid IPv4 Addresses
1.
192.168.1.1: Common private network address.
2.
8.8.8.8: Google's public DNS server.
3.
10.0.0.254: Another private range address.
4.
172.16.0.1: Within the private range (172.16.0.0 -
172.31.255.255).
5.
203.0.113.10: A documentation-reserved address.
Five Invalid IPv4 Addresses
1.
256.0.0.1: Segment value (256) exceeds the maximum
(255).
2.
192.168.1: Missing the fourth segment.
3.
10.0.0.999: Segment value (999) is too large.
4.
172.16.254.3.5: Contains five segments instead of four.
5.
123.45.67.-1: Contains a negative number.
4. Can we compare
HTTP and FTP protocols? Mention their functionality.
Answer:
HTTP (for web pages)
and FTP (for files) both transfer data but differ in purpose, state,
connection, and security; HTTP is stateless, efficient for web content
(port 80/443), while FTP is stateful, ideal for large file transfers (ports
20/21), often requiring authentication and offering specific file management
commands like listing directories, making them suited for different
tasks.
HTTP (HyperText Transfer
Protocol)
·
Functionality: Delivers web pages, images, and other web
content from servers to browsers, forming the backbone of the World Wide Web.
·
Key
Traits:
o Stateless: Each request is independent, though persistent connections
(HTTP/1.1+) help.
o Connection: Uses TCP; can be persistent or non-persistent.
o Ports: 80 (HTTP) and 443 (HTTPS).
o Authentication: Optional, with various methods (Basic,
Digest).
·
Functionality: Uploads and downloads files between
computers and servers, excellent for file management and backups.
·
Key
Traits:
o Stateful: Maintains connection state.
o Connection: Uses two TCP connections: one for control (port 21) and one
for data (port 20).
o Ports: 20 (Data) & 21 (Control).
o Authentication: Required for most operations (username/password).
·
Primary
Use: HTTP for browsing,
FTP for file transfer.
·
State: HTTP is generally stateless; FTP is
stateful.
·
Connections: HTTP uses one; FTP uses two (control &
data).
·
File
Management: FTP has built-in
commands (list, put, get); HTTP relies on extensions or configurations.
·
Security: HTTP becomes secure with HTTPS (TLS/SSL);
FTP is inherently insecure but can use FTPS.
5. How many 16 port
switches are required to connect 31 computers in a network?
(Hint: To
connect all computers, all switches also should be connected among themselves)
Answer:
You need a minimum
of 3 16-port switches to connect 31 computers, as two switches
only offer 30 usable ports (15 per switch plus one uplink), leaving the 31st
computer unconnected, while three switches in a chain (daisy-chained or star) provide
ample ports (around 44 total usable ports) for all computers and inter-switch
links.
Here's the breakdown:
1.
Two
Switches (Not Enough):
·
Switch 1: 15 computers + 1 port for Switch 2 (16 ports used).
·
Switch 2: 15 computers + 1 port for Switch 1 (16 ports used).
·
Total: 30 computers connected (15 + 15). This
leaves the 31st computer without a connection.
Three
Switches (Sufficient):
·
With three switches,
you have 16 ports per switch for 31 computers plus inter-switch connections.
·
You can connect them
in a line (daisy-chain) or star pattern, using ports for computers and links
between switches.
·
For example, in a
daisy chain:
o End Switch 1: 14 computers + 1 uplink (15
ports used).
o Middle Switch: 13 computers + 2 uplinks (15
ports used).
o End Switch 2: 14 computers + 1 uplink (15
ports used).
o Total: 41 usable ports, enough for 31 computers and the necessary
links.
Therefore, 3 switches
are required to ensure all 31 computers and the switches themselves are
connected.
