IPStructure

Module Code: ELEE1157

Module Name: Network Routing Management

Credits: 15

Module Leader: Seb Blair BEng(H) MPhil PGCAP MIET MIHEEM FHEA

What is IPv4?

  • IPv4: Internet Protocol version 4 is a core protocol that defines IP addresses used in networking.
  • 32-bit address space, supporting up to 4.3 billion addresses.
ELEE1157 | Network Routing Management

IPv4 Address Structure

  • IPv4 addresses are written as four octets separated by periods.

  • Example: 192.168.1.1

  • Each octet is an 8-bit binary number (total 32 bits).

    IPv4 Address Example: 11000000.10101000.00000001.00000001

  • Each octet ranges from 0-255 in decimal.

ELEE1157 | Network Routing Management

IPv4 Address Classes

IPv4 addresses are divided into five classes:

Class Range Usage Networks Hosts
A 1.0.0.0 - 126.0.0.0 Large networks 16777216 16777214
B 128.0.0.0 - 191.255.0.0 Medium networks 65534 65534
C 192.0.0.0 - 223.255.255.0 Small networks 2097152 254
D 224.0.0.0 - 239.255.255.255 Multicasting
E 240.0.0.0 - 255.255.255.255 Experimental
ELEE1157 | Network Routing Management

Reserved IP Ranges

IPv4 has reserved addresses for private networks and special purposes.

Range Description
10.0.0.0 - 10.255.255.255 Class A private
172.16.0.0 - 172.31.255.255 Class B private
192.168.0.0 - 192.168.255.255 Class C private
127.0.0.0 - 127.255.255.255 Loopback (localhost)
ELEE1157 | Network Routing Management

Subnetting in IPv4

What is Subnetting?

  • Dividing a large network into smaller, manageable subnetworks.
  • Uses a subnet mask to identify network and host portions.

Example:

  • IP: 192.168.1.0/24

  • Subnet Mask: 255.255.255.0

    Network Portion | Host Portion
192.168.1       | .0 - .255
ELEE1157 | Network Routing Management

CIDR Notation

CIDR (Classless Inter-Domain Routing)

  • Uses slash notation to indicate the subnet mask length (e.g., /24).
  • 192.168.1.0/24 means the first 24 bits are network bits.

Examples of CIDR:

  • /8 (Class A) -> 255.0.0.0
  • /16 (Class B) -> 255.255.0.0
  • /24 (Class C) -> 255.255.255.0
ELEE1157 | Network Routing Management

Example: Calculating Subnets P1

Given Network: whose IP is range is 192.168.1.0/24 create four subnets.

|1. To create four subnets, we need to borrow bits from the host portion

  • Subnet Mask:
    • /26 -> 255.255.255.192 or 11111111.11111111.11111111.11000000
  1. Calculate Number of Subnets and Hosts per Subnet:
    • With /26, the first 26 bits are the network portion, and the remaining 6 bits are for hosts.
    • Number of subnets created: (since we borrowed two bits)
    • Hosts per subnet: $2^6 = 64 $ addresses per subnet (62 usable)
ELEE1157 | Network Routing Management

Example: Calculating Subnets P2

  1. Determine the Subnet Ranges::
  • Starting with 192.168.1.0, each subnet has 64 addresses, incrementing by 64 for each subsequent subnet.
Subnet ID Range Description
192.168.1.0/26 192.168.1.0 - 192.168.1.63 First subnet
192.168.1.64/26 192.168.1.64 - 192.168.1.127 Second subnet
192.168.1.128/26 192.168.1.128 - 192.168.1.191 Third subnet
192.168.1.192/26 192.168.1.192 - 192.168.1.255 Fourth subnet
ELEE1157 | Network Routing Management

Why IPv6?

IPv4 Address Exhaustion

  • IPv4: 32-bit address space (~4.3 billion addresses).

  • Increasing number of internet-connected devices.

  • IPv6: 128-bit address space

  • ~340 undecillion addresses (enough for future needs).

Enhanced features:

  • Auto-configuration.

  • Improved security (IPSec).

  • Simplified header format.

ELEE1157 | Network Routing Management

IPv6 Address Format

center

  • Length: 128 bits (8 groups of 16 bits each).

  • Hexadecimal notation.

  • Groups separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).

Simplification Rules:

  • Remove leading zeros (e.g., 0010 -> 10).

  • Replace consecutive zero groups with :: (only once per address).

ELEE1157 | Network Routing Management

Anatomy of IPv6 address format: Example

ELEE1157 | Network Routing Management
ELEE1157 | Network Routing Management

IPv4 to IPv6 Transition

  • Dual Stack

    • Devices run both IPv4 and IPv6 simultaneously.

    • Allows gradual transition.

center

ELEE1157 | Network Routing Management

  • Tunneling

    • Encapsulates IPv6 packets within IPv4 headers.

    • Examples:

      • 6to4: Automatically assigns an IPv6 prefix to IPv4.

      • Teredo: Tunnels IPv6 over IPv4 using NAT.

ELEE1157 | Network Routing Management

  • Translation

    • NAT64:

      • Maps IPv6 addresses to IPv4 and vice versa.

      • Enables IPv6-only devices to communicate with IPv4 devices.

ELEE1157 | Network Routing Management

IPv4 to IPv6

Step 1: Understand the IPv4 Address

  • Example IPv4: 192.168.0.1
  • Convert to binary:
    • 192 -> 11000000
    • 168 -> 10101000
    • 0 -> 00000000
    • 1 -> 00000001
  • Binary IPv4: 11000000.10101000.00000000.00000001
ELEE1157 | Network Routing Management

Step 2: Map IPv4 to IPv6 Format

  • IPv6 has special prefixes for IPv4-mapped addresses:
    • ::ffff:0:0/96
  • Append the 32-bit binary IPv4 to the ::ffff: prefix.
ELEE1157 | Network Routing Management

Step 3: Convert Binary IPv4 to Hexadecimal

  • IPv4 in binary: 11000000.10101000.00000000.00000001
  • Group into 4-bit chunks:
    • 1100 0000 1010 1000 0000 0000 0000 0001
  • Convert each chunk to hexadecimal:
    • 1100 -> C
    • 0000 -> 0
    • 1010 -> A
    • 1000 -> 8
    • 0000 -> 0
    • 0000 -> 0
    • 0000 -> 0
    • 0001 -> 1
  • Hexadecimal IPv4: C0:A8:00:01
ELEE1157 | Network Routing Management

Step 4: Construct the IPv6 Address

  • Prefix: ::ffff:
  • Hexadecimal IPv4: C0:A8:00:01
  • Combined: ::ffff:C0A8:01
ELEE1157 | Network Routing Management

Examples for Practice

Example 1

Convert the IPv4 address 10.0.0.1 to IPv6.

Solution
  1. Binary conversion:
    • 10 -> 00001010, 0 -> 00000000, 0 -> 00000000 , 1 -> 00000001
    • Binary: 00001010.00000000.00000000.00000001
  2. Hexadecimal conversion:
    • 0000 1010 0000 0000 0000 0000 0000 0001
    • Hexadecimal: A:0:0:1
  3. IPv6 address: ::ffff:A:0:0:1
ELEE1157 | Network Routing Management

Example 2

Convert the IPv4 address 172.16.254.1 to IPv6.

Solution
  1. Binary conversion:
    • 172 -> 10101100, 16 -> 00010000, - 254 -> 11111110, 1 -> 00000001
    • Binary: 10101100.00010000.11111110.00000001
  2. Hexadecimal conversion:
    • 1010 1100 0001 0000 1111 1110 0000 0001
    • Hexadecimal: AC:10:FE:01
  3. IPv6 address: ::ffff:AC10:FE01
ELEE1157 | Network Routing Management

Cheat Sheet

center

ELEE1157 | Network Routing Management

Summary

  • IPv4 is a 32-bit address space with classes for different network sizes.
  • Subnetting divides a network into smaller parts using subnet masks.
  • IPv6 due to exhaustion of IPv4 address spaces
  • CIDR provides flexible subnetting options.
ELEE1157 | Network Routing Management

Internet Assigned Numbers Authority