Section 8: IP Addressing

Internet Protocol (IP) Address

• An assigned numerical label that is used to identify internet communicating devices on a computer network

• Use in Layer 3 (Network Layer) Addressing

  • Between two different networks or subnets

Internet Protocol version 4 (IPv4) Addressing

The most common type of IP addressing used in networks

IPv4 Address

• Decimal representations of a 32-bit binary number

• Written in dotted-decimal notation which is a series of four decimal numbers separated by dots

  • Octets

    • Refers to the four decimal numbers, individually

      • E.g. 172.21.243.67: 4 numbers, 4 octets

    • IPv4 addresses consist of 4 octets, each represents 8 bits of a binary number, total 32 bits

      • Decimals range from 0 to 255

Network and Host Portion

• Portions of IPv4 that are determined by a subnet mask

• Subnet Mask

  • Contains continuous strings of ones (1) and zeros (0)

    • E.g. 255.255.0.0 = 11111111.11111111.00000000.00000000

    • Network portion - 1

    • Host portion - 0

Classes of IPv4 Addresses

• IP addresses are classified into classes depending on the first octet in their address

  • Class A

  • Class B

  • Class C

  • Class D

  • Class E

Class A Address

• First octet: 1 to 127

  • Default subnet mask: 255.0.0.0

    • Possible Hosts: 16.7 million (256 × 256 × 256)

Class B Address

• First octet: 128 to 191

• Default subnet mask: 255.255.0.0

  • Possible Hosts: 65,536 (256 × 256)

Class C Address

• First octet: 192 to 223

• Default subnet mask: 255.255.255.0

  • Possible Hosts: 256

Class D Address

• First octet: 224 to 239

• No default subnet mask

• Reserved for multicast routing

  • Multicast Address

    • A logical identifier for a group of hosts

Class E Address

• First octet: 240 to 255

• No default subnet mask

• Reserved for experimental use in terms of research and development

  • Possible Hosts: 268 million (reserved)

Subnetting

The process of dividing a larger network into smaller subnetworks

• Classful Subnet Mask

• Classless Subnet Mask

Classful Subnet Mask

Uses default masks associated with specific address classes

Classless Subnet Mask

Uses any subnet mask that is not the default for a specific address class

Classless Inter-Domain Routing (CIDR)

The process of borrowing bits from the host portion to expand the network portion, allowing for smaller subnetworks (Classless Subnet Mask)

CIDR Notation

• Combined notation of IP address and subnet masks (e.g. IP/subnet)

• Default CIDR notations for IP address classes to be considered classful:

  • A - /8

  • B - /16

  • C - /24

IPv4 Address Types (4)

• Public

• Private

• Loopback

• Automatic Private

Public IPv4 Address

• Known as a routable IP address

• Unique identifier assigned to devices on the internet

• Leased or purchased from ISPs

• Globally, managed by Internet Corporation for Assigned Names and Numbers (ICANN)

  • Regional Internet Registries (RIRs)

    • Responsible for managing public IP addresses for different regions

      • North America - ARIN

      • Latin America - LACNIC

      • Africa - AFNIC

      • Asia Pacific - APNIC

      • Europe - RIPE

Private IPv4 Address

• Non-internet routable IP address used within local networks

• Allows communication between devices within the network without using a public IP

• Can be used by anyone at any time, but only within their own LANs

• Network Address Translation (NAT)

• Request for Comments (RFCs)

  • A formal publication from the Internet Engineering Task Force (IETF)

  • Authored by computer scientists who want to document new technologies or standards they are proposing

  • RFC 1918

    • Defines ranges for the private IP addresses

    • Private IP Ranges

      • Class A - 10.x.x.x (e.g. 10.0.0.0 - 10.255.255.255)

      • Class B - 172.16.x.x to 172.31.x.x (e.g. 172.16.0.0 - 172.31.255.255) *

      • Class C- 192.168.x.x (e.g. 192.168.0.0 - 192.168.255.255)

Network Address Translation (NAT)

• Method used to translate private IP addresses into public IP addresses and vice versa

• Facilitates local and public network communications

• Conserves global IP address space

Loopback Address (Local Host)

• Specialized IP address assigned as 127.0.0.1

• Used for any higher level protocol can send data back to the host itself without going out to a switch or router

  • Internal testing and troubleshooting

• Entire 127.x.x.x range reserved for loopback purposes

  • Almost always written as 127.0.0.1

  • Other IP addresses inside 127.x.x.x are wasted as part of loopback or local host range

• Local Host

  • The human readable name for the IP address 127.x.x.1

Automatic Private IP Address (APIPA)

• Dynamically assigned by OS when DHCP server is unavailable

• Range - 16.254.0.0 to 16.254.255.255 (169.254.x.x)

• Used as a fallback for network configurations

• Indicates a DHCP issue if assigned to a device

• Dynamic Host Configuration Protocol

  • Assigns dynamic IP addresses to devices

  • Process - DORA

    • Discovery

    • Offer

    • Request

    • Acknowledgement

IPv4 Address Types Exam Tips

• Understand distinctions between public and private IP addresses (routable vs non-routable)

• Memorize ranges for private IP addresses (RFC 1918)

• Be aware of loopback/local host, and APIPA addresses

• Recognize DHCP issues indicated by APIPA addresses

IPv4 Data Flows(3)

• Unicast

• Multicast

• Broadcast

Unicast

• Data from single source to single destination

• Two-way conversation between sender and receiver

Multicast

• Data from single source to multiple specific destinations

• Sender communicates with a specific group of receivers

Broadcast

• Data goes from single source to all sources on a destination network

• Sender addresses all devices on the network

Multicast vs. Broadcast

• Broadcast - EVERYONE receives the message

• Multicast - only those OPTED IN the multicast group receive the message

IPv4 Address Assignments (2)

• Static

• Dynamic

Static Assignment

• Manually inputting IP address, subnet mask, default gateway, and DNS server

• Impractical

  • Prone to errors

  • Time-consuming

Dynamic Assignment

• Quicker, easy, and less error-prone method

• Commonly used for large or small networks

• Utilizes DHCP (Dynamic Host Configuration Protocol) for automatic assignment

Components of a Fully Configured Client *

• IP Address

• Subnet Mask

• Default Gateway (often the router’s IP)

• DNS Server (or WINS server in Window domains)

  • DNS (Domain Name System)

    • Converts domain names to IP addresses for internet communication

    • Acts like an internet phonebook

  • WINS (Windows Internet Name Service)

    • Identifies NetBIOS systems on a TCP/IP network and converts those NetBIOS names to IP addresses

    • Works similar to DNS but within Windows domain environment

Methods of Dynamic Assignment (4)

• BOOTP

• DHCP

• APIPA

• ZeroConf

Bootstrap Protocol (BOOTP)

• Older and least used method, orginally for diskless Unix workstations

• Dynamically assigns IP addresses and allows a workstation to load a copy of the boot image over the network

• Uses static database of IP and MAC addresses

Dynamic Host Configuration Protocol (DHCP)

• Modern replacement for BOOTP

• Dynamically assigns IPs based on assignable scope and allows configuration of numerous options with it

• Gives all of the variables including the components of a fully configured client

Automatic Private Internet Protocol Addressing (APIPA)

• Used if DHCP fails

• Assigned self-assigned IPs

• Quick configuration of a LAN without the need for a DHCP server

• Uses private IPs that cannot be routed outside LAN

• Cannot communicate with non-APIPA devices

Zero Configuration (ZeroConf)

• Newer technology based on APIPA, providing the same features and some new ones

• Features

  • Assigns IPv4 link local addresses

  • Utilizes MDNS (Multicast Domain Name Service) for name resolution without DNS

  • Enables service discovery on the network

• Implementations

  • Apple Products

    • Known as Bonjour

    • Used for service discovery

  • Microsoft Windows

    • LLMNR (Link Local Multicast Name Resolution)

    • Extends APIPA for name resolution and service discovery

  • Linux

    • Implemented using SystemD, specifically the SystemD Resolved background service

Number Systems

• Computers use binary (base-2) numbering

• Humans typically use decimal (base-10) numbering

Binary to Decimal Conversiton

• Binary numbers are converted to decimal by summing the powers of 2 for each digit

• Example: Converting 10010110 to decimal

  • 128+16+4+2 = 150

• 1 indicates presence, 0 indicates absence

• Sums up to values of all positions with 1

Decimal to Binary Conversion

• Decimal numbers are converted to binary by repeatedly dividing by 2 and noting remainders

• Example: 167 to binary

  • Subtract highest power of 2 possible, repeating until remainder is 0

  • Each subtraction corresponds to placing a 1 or 0 in the binary representation

    • 167 - 128 = 38 : 1

    • 39 - 64 = x : 0

    • 39 - 32 = 7 : 1

    • 7 - 16 = x : 0

    • 7 - 8 = x : 0

    • 7 - 4 = 3 : 1

    • 3 - 2 = 1 : 1

    • 1 - 1 = 0 : 1

  • 10100111 - binary of 167

Conversation Verification

• To ensure accuracy, check the result by reversing the conversion process

• Add up the decimal values corresponding to the 1s in the binary representation

• Verify that the sum matches the original decimal number

• Example: 10100111 - binary of 167

  • 128 + 32 + 4 + 2 + 1 = 167

Subnetting

• Involves dividing a large network into smaller networks for better management/optimization

• It is crucial for efficient use of IP addresses, both public and private

Subnet Masks

• Modify network sizes by borrowing bits from the host portion and adding them to the network portion

• Default classful subnet masks are rarely optimal for network sizes, so custom subnet masks are used for better efficiency

Subnetting Formulas

• Number of Subnets

  • 2^S

    • S = number of borrowed bits

  • Example: 255.255.255.128 OR /25

    • 2¹ = 2 subnets

      • 1 = number of borrowed bits

• Assignable IP Addresses per Subnet

  • 2^h - 2

  • h = number of host bits

  • "-2” represents the network ID (first) and broadcast ID (last) that need to be taken away when calculating the number of usable IPs

  • Example: 255.255.255.128 OR /25

    • 2⁷ - 2 = 126 assignable addresses

      • 7 = left over bits in the host portion
        

Classful vs. Subnetted Networks

• Classful networks (e.g. /8, /16, /24) have fixed sizes

• Subnetted networks allow flexibility in network size by borrowing bits from the host portion

Variable Length Subnet Mask (VLSM)

• Allows subnets of various sizes to be used within a larger network

• Enhances flexibility in subnetting by accommodating different network requirements

Subnetting Exam Tips

• Memorize the chart correlating subnet mask notation (/24, /25, /26 etc.) with the number of subnets and assignable IP addresses

• Helps to quickly answer subnetting questions by understanding the relationship between subnet size and IP allocation

• Practice subnetting questions, especially in Class C range (/24 - /30)

• Familiarize yourself with CIDR notation and subnetting calculations to excel in subnetting questions on exams

IPv4 Limitations

• Limited address space of only 32 bits of addressable space

  • 4.3 billion addresses

• Address exhaustion due to waste and subnetting

IPv6 Advantages

• 128-bit addresses

  • 340 undecillion addresses

• Solved address exhaustion problem

IPv6 Features

• No broadcasts

• No packet fragmentation

• Simplified header with only 5 fields

• No maximum transmission units (MTUs) for discovery

IPv6 Address Notation

• Hexadecimal Notation

  • 16 possible characters

  • Represented in segments of 4 hexadecimal digits, separated by colons

  • 0 - 9, A - F

    • F can represent 10 - 15

• No more than 32 hexadecimal digits

  • Use of shorthand notation to shorten addresses

    • Four consecutive zeros can be represented by one zero

      • 2018: 0000: 0000: 0000: 0000: 4815: 54ae

        • → 2018: 0: 0: 0: 0: 4815: 54ae

    • Double colon (::) can summarize multiple segments that have just zeros but it can only be used once within a address

      • 2018: 0: 0: 0: 0: 4815: 54ae

        • 2018 :: 4815: 54ae

    • Eliminate leading zeros within segments

Identifying IPv6 Addresses

• IPv4 - Dotted decimal notation (0-255)

• IPv6 - Hexadecimal (0-9, A-F) with colons, in groups of four

• MAC - always have 12 hexadecimal digits, separated by colons, and grouped in pairs of two

IPv6 Address Types (3)

A single interface can be assigned to multiple IPv6 addresses, can be a mixture of address types

• Unicast

• Multicast

• Anycast

IPv6 Unicast

• Identifies a single interface

  • Globally routed unicast addresses

    • Similar as in IPv4

    • 2000-3999

    • First segment in IPv6 address

  • Link Local addresses

    • Like private IP in IPv4 that can only be used in LAN

    • Begins with FE80 as first segment

• Data Flow

  • Similar to IPv4, but with IPv6 addresses

IPv6 Multicast

• Identifies a group of interfaces

• Starts with FF as the two digits within the first segment

• Data Flow

  • Uses multicast groups like in IPv4 (e.g. FF00::A

  • Data travels from a single source (server) to multiple specific destination devices

IPv6 Anycast

• Identifies a set of interfaces

• Allocated for unicast space

• Data Flow

  • Unique to IPv6, replaces broadcast from IPv4

  • Allows one host to update router tables for a group of other hosts

  • IPv6 determines the closest gateway and sends packets as though it was a unicast communication

  • Routers in the group update their tables, improving efficiency

Stateless Address Autoconfiguration (SLAAC)

• An auto-configuration that eliminates the need to obtain addresses or configuration information from a central server

  • Utilizes MAC addresses to create unique identifiers

  • Extended Unique Identifiers (EUI)

    • Allows a host assign itself itself a unique 64-bit IPv6 interface identifier (EUI-64)

  • DHCPv6 can also be used to assign addresses

Neighbor Discovery Protocol (NDP)

• Used to determine Layer 2 addresses on the network

• Functions:

  • Router solicitation

  • Router advertisement

  • Neighbor solicitation

  • Neighbor advertisement

  • Redirection

• Simplifies network configuration and improves efficiency

IPv4 and IPv6 Compatibility Requirements

• IPv6 was designed to be backward compatible with IPv4

• Both protocols can co-exist on the same network to facilitate a smooth transition

Dual Stack

• A network architecture that allows coexistence and simultaneous operation of IPv4 and IPv6 on the same network

• Devices are configured to understand and process IPv4 and IPv6 addresses

• Enables gradual migration to IPv6 while ensuring compatibility and communication between both protocols

  • Preference for IPv6

    • With fallback to IPv4 if IPv6 is not available or supported by the destination

Tunneling

• Method that enables communication of one network protocol within another by encapsulating packets

• Crucial for transitioning from IPv4 to IPv6, allowing IPv6 packets to traverse IPv4 infrastructure

• Encapsulation

  • IPv6 packet will be encapsulated within IPv4 packet at the source or entry point

• Decapsulation

  • Original IPv6 packet will be decapsulated at the tunnel’s endpoint, and delivered to its intended IPv6 destination

  • Tunnel endpoints configuration

    • Static tunnels

    • Dynamic tunnels

• Enables the secure and transparent transportation of data through an incompatible network

NAT64

• A network address translation mechanism allowing IPv6-only devices to communicate with IPv4 servers

• Crucial in environments where dual stack configuration is not feasible

• Translates IPv6 addresses into IPv4 addresses and vice versa, facilitating interoperability

• Helps to conserve remaining IPv4 addresses by allowing multiple IPv6 devices to share a single IPv4 address

• Utilizes a NAT64 gateway at the edge of the IPv6 network to manage translations seamlessly