Routers and Routing Basic Module 1

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Routers and
Routing Basic
Paulo Elmer Q. Vasquez

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Course No. IT 301 Lecture and Laboratory
Course Code Networking 301 and 301L
Descriptive Title Routers and Routing Basic
Credit Units 3
Academic Year/Term 1st
Sem. 2020 - 2021
Mode of Delivery Online/Offline Learning
Name of
Instructor/Professor
Course Description This course introduces the concepts of networking and its
protocols and learning on the components and operations
of routers and switches that includes IP addressing in a
small network. In this module, students will learn how to
configure a router and a switch for basic functionality.
Course Outcomes 1. Define and describe packets in the network.
2. Define the concept of IP addressing and
subnetting.
3. Configure routers and switches using LAN and WAN
interfaces.
4. Configure and troubleshoot basic operations of
routers in a small routed (simulated)network.
SLSU Vision A high-quality corporate science and technology university.
SLSU Mission SLSU will 1) produces S and T Leaders and competitive
professionals; 2) generate breakthrough research in S and
T based disciplines; 3) transform and improve the quality of
life in the communities in the service areas; and 4) be self-
sufficient and financially viable.
Module Guide
The module is composed of seven series of lessons with
activities and explanations with examples. This module is
designed based on 4A’s learning model. Lesson 1 to 6 covers
detailed topics of midterm period for the semester. While
lesson 6 to 12 was intended for final term of the course
subject. Moreover, the content of this learning materials is
a combination of a module and a laboratory manual.
Therefore, students who wanted to learn on networking with
Router and its Basic routing, this module is designed to
develop your skill and ability.

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Networks allow people to communicate, collaborate, and interact in many ways.
Networks are used to access web pages, talk using IP telephones, participate in video
conferences, compete in interactive gaming, shop using the Internet, complete online
coursework, and more. A network can be wired or wireless connection called networking. In
this lesson, we will be discussing the concept of networking.
To help you prepare for our topic, let us figure out your idea about
networking.
Let’s BEGIN!
Introduction to Networking
Lesson 1
a. Define what computer networking is.
b. Describe how things transmit form end-to-end.
Objectives:
At the end of the lesson, learners will be able to:

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We all know that the only way to access our friend’s Facebook page is through
Internet. We had fun talking to them using Messenger. But no one knows the concept and
process of the connections unless you learn.
We usually heard “networking” from people everywhere for faster dissemination of
products. Technology also offers networking for our computers. Let us define networking for
deeper understanding.
• Networking is referred as connecting computers electronically for the purpose of
sharing information. Resources such as files, applications, printers and software are
common information shared in a networking.
• The advantage of networking can be seen clearly in terms of security, efficiency,
manageability and cost effectiveness as it allows collaboration between users in a
wide range.
• Network consists of hardware component such as computer, hubs, switches, routers
and other devices which form the network infrastructure. These are the devices that
play an important role in data transfer from one place to another.
There are two common types of Network:
1. LAN or Local Area Network
Here are the three characteristics of LANs:
• LANs are in a narrower geographic scope (office, campus, school, and home
area).
Almost 4.57 billion people were active internet users as of July 2020.
Let’s DISCUSS!
What do you think they are doing?
________________________________________
______________________________________________
______________________________________________
______________________________________________
______________________________________________
____________________________________

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• LANs have higher data transfer speeds.
• LANs can be used properly without telecommunication lines.
Figure 1.1. Single LAN
Figure 1.2. Multiple LANs
2. WAN or Wide Area Network
Here are the three characteristics of WANs:
■ WANs generally connect devices that are separated by a broader geographic area
than can be served by a LAN.
■ WANs use the services of carriers, such as telephone companies, cable companies,
satellite systems, and network providers.
■ WANs use serial connections of various types to provide access to bandwidth over
large geographic areas.

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Figure 1.3. WAN
What happen in between the connection of two communicating computers?
Network models are here to explain!
1. OSI (Open Systems Interconnection) Layer Model
When computers were first linked together into networks, moving
information between the different types of computers was a formidable task. In the
early 1980s, the International Standards Organization (ISO) recognized the need for
a standard network model. This would help vendors to create interpretable network
devices. The Open Systems Interconnections (OSI) reference model was released and
became the primary architectural model for inter-computer communications.

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2. TCP/IP Model Layer
Application Layer • Provides applications with standardized data exchange.
Transport Layer • Responsible for maintaining end-to-end communications across
network.
Network Layer • Deals with packets and connects independent networks to
transport the packets across network boundaries.
Physical Layer • Operate only on a link—the network component that
interconnects nodes or hosts in the network.
Application
Layer
• It provides user interface & supports for services such
as e-mail, file transfer, access to the world wide web.
• It provides services to different user applications.
Presentation
Layer
• It is concerned with the syntax & semantics of the
information exchanged between the two devices.
• It was designed for data encryption, decryption and
compression.
Session Layer
• It has the responsibility of beginning, maintaining and
ending the communication between two devices,
called session.
• It also provides for orderly communication between
devices by regulating the flow of data.
Transport
Layer
• Implements reliable internetwork data transport
services including flow control, multiplexing, virtual
circuit management, and error checking and recovery.
Network
Layer
• This layer ensures that the packets gets its point of
origin to its final destination.
• It is responsible for the source to destination delivery
of a packet across multiple networks.
Data Link
Layer
• Translates messages from the higher layers into bits
for Physical layer to process.
• It receives the data from network layer and creates
FRAMES, add physical address to these frames & pass
them to physical layer.
Physical Layer • Sends and receives bits or signals on the wire.
E
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I know you are an avid fan of Ivana Alawi and you are downloading her pictures from her
Facebook page. Don’t you?
Application
Layer
Presentation
Layer
Session Layer
Transport
Layer
Data (picture) are broken into pieces called SEGMENTS. This
layer encapsulates the Source and Destination port address
and forward it to the lower layer.
Network
Layer
This layer encapsulates the source and destination IP address
and segments turn into PACKETS. Then, forward it to the
lower layer.
Data Link
Layer
This layer encapsulates source and destination MAC address
called FRAMES. Forward it to the lower layer.
Physical Layer
E
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A
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Sends through bits or signals to your device, undergo
Decapsulation and ready to print.
Network models might be confusing. For better understanding, we will follow the
process of Data Encapsulation which means to enclose data like inserting a letter
to an envelope.
S/D Port DATA
S/DP DATA
sIP/dIP
S/DP DATA
sIP/dIP
sMac/dMac
DATA

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Characteristics of a Network
The are many key structures and performance-related characteristics referred to when
discussing networks:
• Topology:
o Physical topology is the arrangement of the cables, network devices, and end
systems. It describes how the network devices are actually interconnected
with wires and cables.
o Logical topology is the path over which the data is transferred in a network.
It describes how the nework devices appear connected to network users.
• Speed: Speed is a measure of data rate in bits per second (b/s) of a given link in the
network. Although the term “speed” is commonly used when referring to the network
bandwidth, it is not technically accurate. The actual speed tha the bits are
transmitted does not vary over the same medium. The difference in bandwidth is due
to the number of bits transmitted per second, not how fast thay travel over a wire or
wireless medium.
• Cost: Cost indicates the general expense for purchasing of network components, and
installation and maintainance of the network.
• Security: Security indicates how protected the network is, including the information
that is transmitted over the network. The subject of security is important, and
techniques and practices are constantly evolving. Consider security whenever
actions are taken that affect the network.
• Availability: Availability is a measure of the probability that the network is available
for use when it is required.
• Scalability: Scalability indicates how easily the network can accommodate more
users and data transmission requirements. If a network design optimized to only
meet current requirements, it can be very difficult and expensive to meet new needs
when the network grows.
• Reliability: Realiability indicates the dependability of the components that make up
the network, such as the routers, switches, PCs, and servers. Realiability is often
measured as a probability of failure or as the mean time between failures (MTBF).

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Activity 1: Identify the given network. Write LAN for Local Area Network and WAN for Wide
Area Network.
3. 4.
Type of Network: ___________________
How do you know?
_____________________________
___________________________________
___________________________________
___________________________________
___________________________________
___________________________________
__________________________.
Type of Network: ___________________
How do you know?
_____________________________
___________________________________
___________________________________
___________________________________
___________________________________
___________________________________
__________________________.
Type of Network: ___________________
How do you know?
_____________________________
___________________________________
___________________________________
___________________________________
___________________________________
___________________________________
__________________________.
Let’s Answer!

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Activity 2. Write the sequence of OSI Layer model in decapsulation process. Put an arrow in
between boxes.

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Laboratory Activity. In a packet tracer, create 2 LANs connected to WAN using the given
devices. Use the right cable (No Auto cable).
Given: 2 routers, 1 router(as WAN), 2 serial cables, 2 switches, 2 network printers, 6 PCs divide
into 2

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Refences:
https://www.pearsonhighered.com/assets/samplechapter/1/5/8/7/1587132052.pdf
https://unacademy.com/lesson/lesson-8-layered-tasks/SYGU8NJY
http://www.steves-internet-guide.com/internet-protocol-suite-explained/

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We have learned from our previous topic and we clearly understand how data is
transferred in the network to the other end. This lesson will introduce a protocol that enable
us to connect and communicate even in the complex networks.
To help you prepare for our topic, let us answer and figure out your idea in IP
addressing.
Let’s send a letter: Write your information as a sender and your prospected
recipient.
Let’s BEGIN!
Understanding IP Addressing
Lesson 2
a. Define the function of IP address in the network.
b. Identify the class and ranges of an IP address.
Objectives:

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What is an IP Address?
• IP address is a shorter way of saying “Internet Protocol address.” IP addresses are
the numbers assigned to computer network interfaces.
Why DO WE NEED IP ADDRESSES?
• IP addresses are the numbers that enable our computers, servers, telephones,
cameras, printers and sensors to communicate with each other.
• Without the IP addresses assigned to our computers, we would have to send paper
letters and memos instead of sending emails.
Classful IP Address
To provide the flexibility required to support networks of varying sizes, the Internet
designers decided that the IP address space should be divided into three address classes -
Class A, Class B, and Class C.
Class A Networks (/8 Prefixes)
IP address belonging to class A are assigned to the networks that contain a large
number of hosts.
• The network ID is 8 bits long.
• The host ID is 24 bits long.
There are almost 2.7 million emails are sent per second.
Let’s find out how it happen?
Let’s DISCUSS!

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The higher order bit of the first octet in class A is always set to “0”. The remaining 7 bits
in first octet are used to determine network ID. The 24 bits of host ID are used to determine
the host in any network. Therefore, class A has a total of:
• 2^7-2= 126 network ID (Here 2 address is subtracted because 0.0.0.0 is reserved for
default route and 127.0.0.0 is reserved for the loopback function.)
• 2^24 – 2 = 16,777,214 host ID
IP addresses belonging to class A ranges from 1.0.0.0 – 126.255.255.255
Class B Networks (/16 Prefixes)
IP address belonging to class B are assigned to the networks that ranges from medium-
sized to large-sized networks.
• The network ID is 16 bits long.
• The host ID is 16 bits long.
The higher order bits of the first octet of IP addresses of class B are always set to “10”.
The remaining 14 bits are used to determine network ID. The 16 bits of host ID is used to
determine the host in any network. Class B has a total of:
• 2^14 = 16384 network address
• 2^16 – 2 = 65534 host address
IP addresses belonging to class B ranges from 128.0.0.0 – 191.255.255.255
Class C Networks (/24 Prefixes)
IP address belonging to class C are assigned to small-sized networks.
▪ The network ID is 24 bits long.
▪ The host ID is 8 bits long.
7 Bit 24 Bit
Host
Network
0
Network
Number
Host Number
14 Bit 16 Bit
Host
Network
1 0
Network Number Host Number

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The higher order bits of the first octet of IP addresses of class C are always set to 110.
The remaining 21 bits are used to determine network ID. The 8 bits of host ID is used to
determine the host in any network.
▪ 2^21 = 2097152 network address
▪ 2^8 – 2 = 254 host address
IP addresses belonging to class C ranges from 192.0.0.0 – 223.255.255.255
Class D Networks
IP address belonging to class D are reserved for multi-casting. The higher
order bits of the first octet of IP addresses belonging to class D are always
set to 1110. The remaining bits are for the address that interested hosts
recognize.
IP addresses belonging to class D ranges from 224.0.0.0 – 239.255.255.255.
Class E Networks
IP addresses belonging to class E are reserved for experimental and research
purposes. IP addresses of class E ranges from 240.0.0.0 – 255.255.255.255. The
higher order bits of first octet of class E are always set to 1111.
28 Bit
Host
Network
1 1 1 0
28 Bit
Host
Network
1 1 1 1
21 Bit 8 Bit
Host
Network
1 1 0
Network
Number
Host
Number
More Subnets, Less Hosts! More Hosts, Less Subnets!

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Within the address range of every IPv4 network segment have three address types:
10.0.1.0
10.0.1.1
.
.
.
.
.
.
10.0.1.254
10.0.1.255
Network address
The address by which we refer to the network segment (like area code).
All addresses in a network have the same network address bits (same
area code within the same region.
Host address
The addresses assigned to hosts in the network segment. Each host has
a unique address.
Broadcast address
A special address used to send data to all hosts in the network segment.

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Activity 1. Find the class, network and host address for:
1. 220.64.144.2
Class ______
Network Address _______
Host Address ______
2. 10.0.0.2
Class ______
Host Address ______
3. 181.100.15.9.
Class ______
Host Address ______
4. 54.22.155.0.
Class ______
Host Address ______
5. 193.5.2.254
Class ______
Host Address ______
Let’s ANSWER!

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Activity 2: Following the concept of the Peer-to-peer connection, answer the following
questions.
A. Write T if the statement is true, F if false.
1. Can PC 1 send packets to PC 4? ______
B. Fill in the box.
PC IP Class First Host Address Last Host Address Broadcast Address
PC0
PC1
PC2

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References:
https://www.geeksforgeeks.org/introduction-of-classful-ip-addressing/
https://pages.di.unipi.it/ricci/501302.pdf

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We have learned from our previous activity that a peer-to-peer connection is limited
to the same network address. To be able to establish a connection to any other network
addresses, we need a device called router to manage connections termed routing. This
lesson will help us learn about the routing device.
To help you prepare for our topic, let us figure out your idea about the
router.
The only way to reach the outer space is
through Spaceships.
The only way to reach the internet space
is through Routers.
Let’s BEGIN!
The Routers
Lesson 3
a. Identify router components and its functions.
b. Explain how routers manages the network.
Objectives:

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What is Router?
• Is a computer which has the following components:
o Central Processing Unit (CPU)
o Operating System
o Memory and Storage (RAM, ROM, NVRAM, Flash, and Hard drive)
• Basic backbone for the internet.
Let’s DISCUSS!
Let’s talk!
Routers are an important piece of technology that most of us have in our homes, but
many of us don't really understand them. In fact, most people don't even realize what a router
technically is and how it's different from a modem.
To put it simply, a router connects devices within a network by forwarding data packets
between them. This data can be sent between devices, or from devices to the internet. The router
does this by assigning a local IP address to each of the devices on the network. This ensures that
the data packets end up in the right place, rather than getting lost within the network.

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Here are pictures of a router:
Memory and Storage of a Router:
• Random- access memory (RAM): Provides temporary storage for various applications
and processes including IOS, the running configuration file, various tables (i.e., IP
routing table, Ethernet ARP table) and buffers for packet processing.
• Read- only memory (ROM): Provides permanent storage for bootup instructions,
basic diagnostics software, and a limited IOS in case the router cannot load the full-
featured IOS.
• Nonvolatile random- access memory (NVRAM): Provides permanent storage for the
startup configuration file (startup- config).
• Flash memory: Provides permanent storage for the IOS and other system- related
files. The IOS is copied from flash into RAM during the bootup process.

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Routers Choose Best Paths
Primary functions of a router:
• Determine the best path to send packets.
• Forward packets toward their destination.
This time of pandemic, “No facemask No Entry” policy is everywhere. You must bring
facemask all the time.
Likewise, sending data on different IP network address will barred you from sending.
You must know the default gateway all the time.
What default gateway is?
H
O
W
?
The router uses its routing table to determine the best
path to use to forward a packet. When the router receives a
packet, it examines the destination address of the packet and uses
the routing table to search for the best path to that network. The
routing table also includes the interface to be used to forward for
each known network. When a match is found, the router
encapsulates the packet into the data link frame of the outgoing
or exit interface, and the packet is forwarded toward its
destination.
G A T E W A Y

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✓ The node in a computer network using the internet protocol suite that serves as the
forwarding host (router) to other networks when no other route specification
matches the destination IP address of a packet.
✓ Identifies the router to send a packet to when the destination is not on the same
local network subnet.
How default gateway work?
❖ When a host sends a packet to a device that is on the same IP network, the packet is
simply forwarded out of the host interface to the destination device.
❖ When a host sends a packet to a device on a different IP network, then the packet is
forwarded to the default gateway, because a host device cannot communicate
directly with devices outside of the local network. The default gateway is the
destination that routes traffic from the local network to devices on the remote
networks. It is often used to connect a local network to the internet.
Device LEDs
• Green LED means a good connection while a blinking green LED indicates network
activity.
• If the link light is not ON, then there may be problem with either the network cable
or the network itself.

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Cisco 1941 LEDs
# Port LED Color Description
1 GE0/0 &GE0/1 S (Speed) 1 blink + pause Port operating at 10 Mb/s
2 blink + pause Port operating at 100 Mb/s
3 blink + pause Port operating at 1000 Mb/s
L (Link) Green Link is active.
Off Link is inactive.
2 Console EN Green Port is active.
Off Port is inactive.
3 USB EN Green Port is active.
Off Port is inactive.

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Console Access
In production environment, infrastructure devices are commonly accessed remotely
by Secure Shell (SSH) or HyperText Transfer Protocol Secure (HTTPs). If remote access fails,
console access is really only required when initially configuring a device.
Console access requires:
• Console cable: RJ-45-to-DB-9 console cable
• Terminal emulation software: Tera Term, PuTTY, and Hyper Terminal
Note: Some laptops and PCs do not come with DB-9 serial port connectors and may
require a USB-to-serial port adapter.

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Activity 1. Essay
Instruction: Write Y if it is a router, N if not. Use the provided space for your answer.
Let’s ANSWER!
Answer: __________
How do you know?
_________________________________________
_________________________________________
_________________________________________
_________________________________________
Answer: __________
How do you know?
_________________________________________
_________________________________________
_________________________________________
_________________________________________
Answer: __________
How do you know?
_________________________________________
_________________________________________
_________________________________________
_________________________________________
Answer: __________
How do you know?
_________________________________________
_________________________________________
_________________________________________
_________________________________________

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References:
http://netcert.tripod.com/ccna/routers/ios.html
https://www.makeuseof.com/tag/technology-explained-how-does-a-router-work/

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SOUTHERN LEYTE STATE UNIVERSITY – San Juan
San Juan, Southern Leyte
6611
Module II
IT 301 – Routers and Routing Basic
By:
Instructor
Academic Year: 2020 – 2021

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A Router is a computer, just like any other computer including a PC. We can impose
password, name it like your own, and many other commands. This lesson will help us to
configure basic settings and start working.
To help you prepare for our topic, ask yourself first of who will you be in
the future.
Let’s BEGIN!
Configure Basic Router Settings
Lesson 1
a. Configure basic router settings.
b. Configure connected interfaces.
Objectives:

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Logging in to the Router
User Mode
• The first prompt will look like Routername> the greater than sign at the prompt tells
you that you are in user mode. In user mode you can only view limited statistics of
the router.
Shortcut commands:
1. Enable – en 3. Interface – int (ex. int fa0/0)
2. Configure terminal – conf t 4. Copy startup-config – wr
Search for more shortcut commands. (Google)
Let’s DO It!
Let’s talk!
Prominent companies are using Cisco routers. Most individuals in the field of
IT, even your “grandpa” aims to be certified. Cisco routers and switches can
only be interfaced in CLI (Command Line Interface). If you aim to become a
system administrator and “I know you can!”, you should practice using CLI and
improve your typing skill.

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Privileged EXEC Mode
• To change configurations, you first need to enter privileged EXEC mode. This is done
by typing enable at the Routername> prompt, the prompt then changes to
Routername#. This mode supports testing commands, debugging commands, and
commands to manage the router configuration files.
• To go back to user mode type disable at the Routername# prompt.
• If you want to leave completely, type logout at the user mode prompt. You can also
exit from the router while in privileged mode by typing exit or logout at the
Routername# prompt.
Global Configuration Mode
• Enter this mode from the privileged mode by typing configure terminal or conf t for
short, the prompt will change to Router(config)#.
• Changes made in this mode change the running-config file in DRAM. Use configure
memory to change the startup-config in NVRAM. Using configure network allows
you to change the configuration file on a TFTP server. If you change the memory or
network config files, the router has to put them into memory (DRAM) in order to
work with them, so this will change your router's current running-config file.
When configuring a Cisco switch or router, the following basic tasks should be performed
first:
Step 1. Name a device: Distinguishes it from other routers.
Step 2. Secure management access: Secures privileged EXEC, user EXEC, and Telnet access,
and encrypts passwords to their highest level

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Step 3. Configure a banner: Provides legal notification of unauthorized access.
Step 4. Save the configuration: To ensure that your settings are not lost.
Configure Router Interface
Step 1. Enter into the interface configuration mode.
Step 2. Add a short description about the interface.
Step 3. Add an IPv4 address and subnet mask.
Step 4. Add a clock rate if it is a serial interface with a DCE cable plugged into it.
Step 5. Activate the interface.

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Example:
Let’s configure this network.
Rautee1:
Configure the Fastethernet 0/0 interface.
Configure the Fastethernet 0/1 interface.

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Assign IP Address to the connected PC.
PC0:
Rautee2:
1. Configure the Fastethernet 0/0 interface
Select

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2. Configure the Fastethernet 0/1 interface
Assign IP Address for:
3. PC1
4. PC2
5. PC3

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Verify connectivity of Directly Connected Networks
The following three commands are especially useful to quickly identify an interface status:
Note: Privileged EXEC Mode
• show ip interface brief: Displays a summary for all interfaces including the
IPv4 address of the interface and current operational status.
• show ip route: Displays the contents of the IPv4 routing table stored in RAM.
In Cisco IOS 5, active interfaces should appear in the routing table with two
related entries identified by the code ‘C’ (Connected) or ‘L’ (Local). In the
previous IOS versions, only a single entry with the code ‘C’ will appear.

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Activity 1. Configure an interface with Classful IP address.
1. R1
2. R2
Let’s ANSWER!

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3. R3
4. PC0
5. PC1
6. PC4
7. PC5

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References:
http://netcert.tripod.com/ccna/routers/ios.html

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We have configured a network with classful IP addresses from our previous lesson.
We found out that each network uses classful IP address which is costly in creating a network.
This lesson will help us extend our network without wasting the classful IP address.
To help you prepare for our topic, let us divide and save boxes from
the puzzle below.
I asked for five (5) equal boxes to use but I received seven (7) equal
boxes. Can you help me create 5 equal boxes without throwing the sticks and saved
2 for later use?
Instruction: Move 3 sticks (only 3) to create 5 boxes.
Let’s BEGIN!
Draw your answer here:
Subnetting with Fixed Length Subnet Mask
Lesson 2
a. Define the concept of subnetting.
b. Configure a network with Classless IP address.
Objectives:

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In the history of networking, network uses only Classful IP Address which result to
the depletion as network grows. This illustration manifests that an IP Classful address can
be divided into parts called subnets to cater according to the needs of the network and save
the rest (as available).
Here comes the subnetting that divides the Classful IP Address into many IP
addresses called Classless IP Address to create more networks. This created solution
manifest the beauty of networking.
Why subnetting was introduced?
• Internet routing table were beginning to grow.
• Local administration had to request another network number from the
Internet before a new network could be installed at their site.
• To divide a single Class A, B, or C network number into smaller pieces.
Figure 1.1. Defining Subnet Mask /Extended Prefix Network in Class C IP Address.
This figure extends the Number of Network from /24 bits to /27 bits to subnet.
Let’s DISCUSS!

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Binary Numbers
• Binary numbers are base 2 numbers (2𝑥
), and have only two values – 0 and 1.
• Convert between binary and decimal is essential for anyone involved in
computers, coding, and networking.
Let us COUNT!
20
= 21
= 22
= 23
= 24
= 25
= 26
= 27
=
1 2 4 8 16 32 64 128
Example 1: Convert 155 to Binary
Answer:
155 − 𝟏𝟐𝟖 = 27, then 27 − 𝟏𝟔 = 11, then 11 − 𝟖 = 3, then 3 − 𝟐 = 1, last 1 − 𝟏 = 0
128 64 32 16 8 4 2 1
1 0 0 1 1 0 1 1
Adding 128+16+8+2+1 is equal to 155. We are giving 1 unit for 128, 1 unit for 16, 1 unit
for 8, 1 unit for 2, and 1 unit for 1. Therefore, 155 is 100011011 in binary.
Example 2: We will convert Class A IP address 105.112.45.60 to Binary Number.
105. 112. 45. 60
0 1 1 0 1 0 0 1 0 1 1 1 0 0 0 0 0 0 1 0 1 1 0 1 0 0 1 1 1 1 0 0
If we add the numbers 64, 32, 8 and 1, we get the total of 105. The same computation to the
2nd up to the 4th octet.
Quick discussion!

46
How to Subnet?
Subnet example#1.
Given:
An organization is assigned the network number 192.168.1.0/24 and it needs to define
six subnets.
My HANDY Chart.
128 64 32 16 8 4 2 1
27
26
25 24
23
22
21
20
Step one: Determine the number of bits required to define the six subnets. Using My HANDY
Chart, 6 subnets is 3 bits long.
Here is HOW!
Step two: Add the original Subnet Mask and the number of Subnets (in BITS)
Here is how, /24 + 3 = /27. Simply extend your Network prefix to /27.
Step two: Extend the network prefix and get the subnet mask in decimal.
128 64 32 16 8 4 2 1
1 1 0
11000001.10101000.00000001.00000000 = 192.168.1.0/24
11000001. 10101000.00000001.00000000 = 192.168.1.0/27
Network Prefix
Extended Network Prefix
Convert all network bits to 1s:
11111111.11111111.11111111.111 00000
Therefore, subnet mask is 255.255.255.224
128+64+31 = 224
Subnets of 3,7,15,31,63,127 need an extra bit, so add ONE bit more!

47
Step three: Plot the Subnets 000 – 101 in binary (0-5) and Convert.
Subnet#0: 11000001. 10101000.00000001.000 00000 = 192.168.1.0/27
Subnet#1: 11000001. 10101000.00000001.001 00000 = 192.168.1.32/27
Subnet#2: 11000001. 10101000.00000001.010 00000 = 192.168.1.64/27
Subnet#3: 11000001. 10101000.00000001.011 00000 = 192.168.1.96/27
Subnet#4: 11000001. 10101000.00000001.100 00000 = 192.168.1.128/27
Subnet#5: 11000001. 10101000.00000001.101 00000 = 192.168.1.160/27
Refer to the example below if you have not mastered the binary to decimal conversion.
Subnet#1: 11000001. 10101000.00000001.001 00000 = 192.168.1.32/27
Subnet#2:1000001. 10101000.00000001.010 00000 = 192.168.1.64/27
0 1 0 0 0 0 0 0
128 64 32 16 8 4 2 1

48
Step four: Plot the number of Hosts of each Subnet from 00001 – 11111 in binary (1-31) and
Convert. In this case, Subnet#2 and #3.
Refer to the example below if you have not mastered the binary to decimal conversion.
Subnet#2: 11000001. 10101000.00000001.010 00000 = 192.168.1.64/27
Host#1: 11000001. 10101000.00000001.010 00001 = 192.168.1.65/27
0 1 0 0 0 0 0 1
128 64 32 16 8 4 2 1
Adding 64 and 1 is equal to 65.
Subnet#2: 11000001. 10101000.00000001.010 00000 = 192.168.1.64/27 – Network address
Host#1: 11000001. 10101000.00000001.010 00001 = 192.168.1.65/27
Host#30: 11000001. 10101000.00000001.010 11110 = 192.168.1.94/27
Host#31: 11000001. 10101000.00000001.010 11111 = 192.168.1.95/27 – Broadcast Address
Subnet#3: 11000001. 10101000.00000001.011 00000 = 192.168.1.96/27- Network address
Host#1: 11000001. 10101000.00000001.011 00001 = 192.168.1.97/27
Host#30: 11000001. 10101000.00000001.011 11110 = 192.168.1.126/27
Host#31: 11000001. 10101000.00000001.011 11111 = 192.168.1.127/27 – Broadcast Address
Usable Host
Address
Usable Host
Address
Up to
Up to

49
Therefore, 192.168.1.0/24 has extended to /27 with the subnets of:
Subnet # 192.168.1.0 192.168.1.32 192.168.1.64 192.168.1.96 192.168.1.128 192.168.1.160
1st
valid IP 192.168.1.1 192.168.1.33 192.168.1.65 192.168.1.97 192.168.1.129 192.168.1.161
Last valid
IP
192.168.1.30 192.168.1.64 192.168.1.94 192.168.1.126 192.168.1.158 192.168.1.190
Broadcast 192.168.1.31 192.168.1.63 192.168.1.95 192.168.1.127 192.168.1.159 192.168.1.191
Another Illustration:
32 64 96 128 160 192 224 255
0 255
Saved Hosts
Let us apply the subnetted IP Address (Classless IP) to a network.

50
R1: Fastethernet0/0
R1: serial0/0/0 (Add clock rate to one side of a serial link only)
Adding Serial Interface to the router.
select
drag
Switch
Off &
On!

51
R1: serial0/0/1
PC0: First Host Address.
PC1: Last Host Address.
1. R2: Fastethernet0/0

52
2. R2: serial0/0/0
3. R2: serial0/0/1
4. PC2: First Host Address.
5. PC3: Last Host Address.

53
7. R3: serial0/0/0
8. R3: serial0/0/1

54
Activity 1. Assume that you have been assigned the 192.168.10.0/24 network block. You
need to establish eight (8) subnets.
1 __________ binary digits (bits) are required to define 8 subnets.
2 Specify the extended network prefix that allows the creation of 8 subnets.
_______________________________________________________
3 Express the subnets in binary format and dotted-decimal notation:
Subnet#0 ____________________________________________________
Subnet #1 ____________________________________________________
Subnet #2 ____________________________________________________
Subnet #6 ____________________________________________________
Subnet #7 ____________________________________________________
4 List the range of host addresses that can be assigned to Subnet #2.
Host#1 _______________________________________________________
Host#2 _______________________________________________________
Host# 29_______________________________________________________
Host#31 _______________________________________________________
Let’s ANSWER!

55
5 What is the broadcast address for Subnet #2?
_______________________________________________________
Refences:

56
We have configured a network using the classless IP addresses from our previous
lesson. With FLSM (Fixed Length Subnet Mask), IP addresses were divided into the same
length and left unused addresses in a point-to-point connection (serial link). This lesson will
help us share the IP addresses according to the need of the network.
To help you prepare for out topic, let us figure out the illustration below.
When lockdown was implemented because of COVID pandemic, the government
ordered the DSWD to give financial assistance to the people affected by the crisis. And, here
are the categorized beneficiaries.
5,000.00 php 1,500.00 php
They received assistance according to the size of a family.
Let’s BEGIN!
Subnetting with Variable Length Subnet Mask
Lesson 3
a. Define the concept of VLSM.
b. Configure a network with VLSM.
Objectives:

57
VLSM stands for Variable Length Subnet Mask where the subnet design uses more
than one mask in the same network which means more than one mask is used for different
subnets of a single class A, B, C or a network. It is used to increase the usability of subnets
as they can be of variable size. It is also defined as the process of subnetting of a subnet.
Let’s do it!!
Subnet example:
Given:
An organization is assigned the network number 192.168.1.0/24 and it needs to define
six subnets.
Step one: Determine the number of bits required by each subnet using My HANDY Chart.
My HANDY Chart.
128 64 32 16 8 4 2 1
27
26
25 24
23
22
21
20
Subnet #0: 6 host bits
Subnet #3: 2 host bits (for point-to-point connection)
60 hosts + 2 (for network and broadcast address)
Let’s DISCUSS!

58
Step two: Take the host bits and leave the remaining bits for network address. Convert the
network address to 1’s and convert to decimal number.
Step three: Take the host bits and leave the remaining bits for network address. Plot the valid
usable IP hosts.
11000001.10101000.00000001.00000000=192.168.1.0/24
Subnet#0: 11000001.10101000.00000001.00 000000=192.168.1.0/26
Subnet Mask: 11111111.11111111.11111111.11 000000 = 255.255.255.192
Subnet #1: 11000001. 10101000.00000001.000 00000=192.168.1.0/27
11111111.11111111.11111111.111 00000=255.255.255.224
Subnet #2: 11000001. 10101000.00000001.0000 0000=192.168.1.0/28
11111111.11111111.11111111.1111 0000=255.255.255.240
Subnet #3: 11000001. 10101000.00000001.000000 00=192.168.1.0/30
11111111.11111111.11111111.111111 00=255.255.255.252
Subnet #4: 11000001. 10101000.00000001.000000 00=192.168.1.0/30
11111111.11111111.11111111.111111 00=255.255.255.252
Subnet #5: 11000001. 10101000.00000001.000000 00=192.168.1.0/30
11111111.11111111.11111111.111111 00=255.255.255.252

59
Subnet Mask
Subnet#0: 11000001. 10101000.00000001. 00 000000 =192.168.1.0 192
00 000001 = 192.168.1.1 192
00 111111 = 192.168.1.63
192
Subnet #1: 11000001. 10101000.00000001. 010 00000 =192.168.1.64 224
010 00001 = 192.168.1.65 224
010 11111= 192.168.1.95 224
Subnet #2: 11000001. 10101000.00000001. 0110 0000 =192.168.1.96 240
0110 0001 = 192.168.1.97 240
0110 1111 = 192.168.1.111 240
Subnet #3: 11000001. 10101000.00000001. 011100 00 = 192.168.1.112
252
011100 01= 192.168.1.113
252
011100 11= 192.168.1.115
252
Subnet #4: 11000001. 10101000.00000001. 0111 01 00 = 192.168.1.116
252
0111 01 01= 192.168.1.117
252
0111 01 11= 192.168.1.119
252
Subnet #5: 11000001. 10101000.00000001. 011110 00= 192.168.1.120

60
Adding Serial Interface to the router.
select
drag
Switch
Off &
On
Let us configure a network with Variable Length Subnet Mask.

61
R1: Fastethernet0/0
R1: serial0/0/0
R1: serial0/0/1
PC0: First Host Address.

62
PC1: Last Host Address.
2. R2: serial0/0/0
3. R2: serial0/0/1

63
7. R3: serial0/0/0

64
8. R3: serial0/0/1
32 64 96 128 160 192 224 255
0
Saved Hosts
255

65
Activity 1. Configure a network with Variable Length Subnet Mask.
Given: Assume that you have been assigned the 192.168.10.0/24 network block. You need
to establish five (5) subnets.
Subnet0: 60 hosts
Subnet1: 20 hosts
Subnet2: 4 hosts
Subnet3: 2 hosts
Subnet4: 2 hosts
1. R1:
Serial interface (3pts)
Fastethernet (2pts)
Let’s ANSWER!

66
PC0 (2pts)
PC1 (2pts)
2. R2:
Fastethernet (2pts)
PC2 (2pts)
PC3 (2pts)

67
3. R1:
Fastethernet (2pts)
PC4 (2pts)
PC5 (2pts)

68
References:

Routers and Routing Basic Module 1

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