Virtual Laboratory: Internet Protocol (IP)

Internet Protocol (IP) Fundamentals

Overview

Internet Protocol (IP) is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking and essentially establishes the Internet.

Key Characteristics

Connectionless protocol (no prior connection establishment)
Best-effort delivery (no guarantee of delivery)
Media independent (works over any underlying technology)
Logical addressing (IP addresses identify hosts)

IPv4 vs IPv6

Address Length

32 bits (IPv4)

128 bits (IPv6)

Address Space

~4.3 billion

~3.4×10³⁸

Header Size

20-60 bytes

40 bytes fixed

IPv4 Packet Structure

32 bits (4 bytes)

Version (4)

IHL (4)

TOS (8)

Total Length (16)

Identification (16)

Flags (3)

Fragment Offset (13)

TTL (8)

Protocol (8)

Header Checksum (16)

Source IP Address (32 bits)

Destination IP Address (32 bits)

Options + Padding (variable)

DATA PAYLOAD

Version (4 bits)

Indicates the IP version (4 for IPv4, 6 for IPv6). Enables routers to process packets correctly.

TTL (8 bits)

Time To Live. Decremented at each hop. Prevents infinite routing loops. When 0, packet is discarded.

Protocol (8 bits)

Identifies the next-level protocol (TCP=6, UDP=17, ICMP=1). Determines payload handling.

IP Addressing & Subnetting

Classful Addressing (Legacy)

Class	Range	Default Mask	Networks
A	1.0.0.0 - 126.0.0.0	/8	128
B	128.0.0.0 - 191.255.0.0	/16	16,384
C	192.0.0.0 - 223.255.255.0	/24	2,097,152

CIDR (Classless Inter-Domain Routing)

Replaced classful addressing to improve address space utilization and routing scalability.

192.168.1.0/26

Network: 192.168.1.0

Mask: 255.255.255.192

Hosts: 62 (2⁶ - 2)

Range: 192.168.1.1 - 192.168.1.62

Interactive Subnetting

IP Address

CIDR Prefix (/n)

/1 /24 /30

Visual Subnet Map

Enter IP and CIDR to visualize subnet allocation

Network

Usable

Broadcast

IP Address Converter

Decimal IP Address

. . .

Binary to Decimal

32-bit Binary (grouped by octets)

Bitwise Operations Visualizer

IP Address

Subnet Mask

Operation Result (AND)

Visual Bitwise AND Operation:

Laboratory Procedure

Experiment 1: IP Address Analysis

Objective: Understand IPv4 address structure and identify address classes.

Open the Binary/Decimal Converter simulation
Enter the IP address: 172.16.0.1
Convert to binary and record the first 4 bits of the first octet
Identify the address class (A, B, or C) based on the binary prefix:
- Class A: 0xxx (0-127)
- Class B: 10xx (128-191)
- Class C: 110x (192-223)
Repeat for addresses: 10.0.0.1, 192.168.1.1, 223.255.255.1

Experiment 2: Subnetting and CIDR

Objective: Calculate subnet parameters and understand CIDR notation.

Navigate to the Subnetting Calculator
Enter network address: 192.168.10.0
Set CIDR to /26 (255.255.255.192)
Record the following parameters:
- Number of usable hosts per subnet
- Number of possible subnets
- Broadcast address
- Host range
Change CIDR to /30 and observe the change in usable hosts
Explain why /30 is commonly used for point-to-point links

Experiment 3: IP Packet Structure Analysis

Objective: Analyze IPv4 header fields and understand packet encapsulation.

Open the Packet Analyzer simulation
Build a packet with:
- Source: 192.168.1.5
- Destination: 192.168.1.10
- TTL: 64
- Protocol: TCP (6)
Observe the header fields and their binary representation
Calculate the header checksum (observe the field)
Modify the TTL value and observe how it affects the header
Change protocol to UDP and note the protocol field change

Experiment 4: Routing Logic

Objective: Understand longest prefix match and routing decisions.

Launch the Routing Simulation
Examine the routing table entries
Test the following destination addresses and record the next hop:
- 192.168.1.50 (local network)
- 10.0.5.20 (remote network)
- 8.8.8.8 (internet/default route)
Explain why the router chose specific paths
Describe the concept of "longest prefix match" using your results

Experiment 5: Advanced Subnetting (VLSM)

Objective: Design a subnetting scheme using Variable Length Subnet Masking.

Given network: 172.16.0.0/16
Requirements:
- Subnet A: 500 hosts
- Subnet B: 200 hosts
- Subnet C: 100 hosts
- 3 point-to-point links (2 hosts each)
Calculate the required CIDR for each subnet
Use the calculator to verify your calculations
Create a subnet allocation table showing network address, mask, and range for each

Safety & Best Practices

Double-check all binary-to-decimal conversions
Remember that usable hosts = 2^(host bits) - 2 (network and broadcast addresses reserved)
When subnetting, always account for future growth
Document all calculations step-by-step for verification

Laboratory Report Guidelines

Report Structure

Cover Page

Experiment title, course name, student name, ID, date, instructor name

Objectives

Clear statement of what the experiment aims to demonstrate

Theory

Brief summary of IP protocol, addressing, and subnetting concepts

Equipment/Tools

Virtual laboratory software, calculator, simulation parameters

Content Requirements

Procedure

Step-by-step description of experiments performed

Observations & Data

All calculated values, screenshots of simulations, binary conversions

Analysis

Interpretation of results, verification of calculations, error analysis

Conclusion

Summary of findings, key learnings, practical applications

Data Recording Tables

Include properly formatted tables for all experiments. Example format:

Experiment	Input Parameters	Calculated Result	Simulated Result	Error %
Subnetting /26	192.168.1.0/26	62 hosts	62 hosts	0%
Binary Conversion	192.168.1.1	11000000...	11000000...	0%

Common Mistakes to Avoid

Forgetting to subtract 2 for network and broadcast addresses
Confusing CIDR notation with subnet mask notation
Incorrect binary-to-decimal conversion (check bit weights)
Ignoring the header length field (IHL) in packet analysis
Not showing step-by-step calculations
Missing units (bits vs bytes) in final answers

Grading Rubric

Completeness of experiments 30%

Accuracy of calculations 25%

Analysis & understanding 25%

Presentation & formatting 20%

Submission Checklist

All 5 experiments completed Screenshots of simulations included All tables filled with data

Calculations shown step-by-step Conclusions address all objectives PDF format, properly named