IP Addressing Study Notes

IP Addressing

Lesson Objectives

  • Explain the use of IPv4 addresses

  • Convert between binary and decimal numbering systems

  • Describe the structure of an IPv4 address including the network portion, host portion, and the subnet mask.

Binary and Decimal Conversion

Numbering Systems

  • Binary Number System: Consists of the numbers 0 and 1, called bits.

  • IPv4 Addresses: Expressed in 32 binary bits divided into 4 octets (8 bits each).

IPv4 Addresses Expressed in Binary

  • Example of a binary IPv4 address: 11010001.10100101.11001000.11100001

  • Example of LAN A Network Address: 11000000.10101000.00001010.00000000/24

  • PC Addressing Examples:

    • PC1: 11000000.10101000.00001010.00000001

    • PC2: 11000000.10101000.00001010.00001010

Positional Value in Binary

  • Illustrated as:

128 64 32 16 8 4 2 1
 Binary Number
   1  0  1  0  0  0  0  0

  • Calculation example: 128 + 64 + 0 + 0 + 0 + 0 + 0 + 0 = 192

  • Result in Dotted Decimal Notation: 192.

Structure of IPv4 Address

  • Hierarchical Structure: Composed of a Network portion and Host portion.

  • All devices on the same network must have the same network portion.

  • Subnet Mask: Helps devices identify the network and host portions.

Example of IPv4 Address Structure

  • IPv4 Address Example: 192.168.10.10

    • Network Portion: 192.168.10

    • Host Portion: 10

    • Binary Representation: 11000000.10101000.00001010.00001010

Address Classes and Subnet Masks

Classful Addressing

  • Addresses classes are defined by the first octet:

    • Class A: 1-126 (Subnet Mask: 255.0.0.0)

    • Class B: 128-191 (Subnet Mask: 255.255.0.0)

    • Class C: 192-223 (Subnet Mask: 255.255.255.0)

    • Class D: 224-239 (Multicast)

    • Class E: 240-255 (Reserved for future use, research and development)

Details of Classful Addressing

Class

Address Range

Network and Host Parts

Default Subnet Mask

Number of Hosts

A

1.0.0.0 - 126.255.255.255

N.H.H.H

255.0.0.0

16 million

B

128.0.0.0 - 191.255.255.255

N.N.H.H

255.255.0.0

65,534

C

192.0.0.0 - 223.255.255.255

N.N.N.H

255.255.255.0

254

D

224.0.0.0 - 239.255.255.255

Multicast address

n/a

n/a

E

240.0.0.0 - 255.255.255.255

Reserved

n/a

n/a

  • Note: Class A addresses 127.0.0.0 to 127.255.255.255 are reserved for loopback, localhost, and diagnostic functions.

Subnet Mask

  • Three IPv4 addresses must be configured on a host:

    1. Unique IPv4 address of the host.

    2. Subnet mask, which identifies the network/host portion of the IPv4 address.

    3. Default gateway, the IP address of the local router interface.

Obtaining IP settings

  • Automatic Assignment: Obtain an IP address automatically.

  • Static Assignment: Use specific IP address, subnet mask, and default gateway.

Types of IPv4 Addresses

Public and Private IPv4 Addresses

  • Public IPv4 Addresses: Globally routed between ISP routers. However, not all available IPv4 addresses can be used on the internet.

  • Private IPv4 Addresses: Blocks of addresses used by organizations to assign IPv4 addresses to internal hosts, introduced due to the depletion of IPv4 address space in the mid-1990s.

  • Not routable, must be translated to a public IPv4 to be routed.

  • Defined by RFC 1918.

Private Address Blocks

  • 10.0.0.0/8: 10.0.0.0 to 10.255.255.255

  • 172.16.0.0/12: 172.16.0.0 to 172.31.255.255

  • 192.168.0.0/16: 192.168.0.0 to 192.168.255.255

IANA Structure for IPv4 Address Distribution

  • Major regions managed by:

    • AfriNIC

    • APNIC

    • ARIN

    • LACNIC

    • RIPE NCC

VLAN Overview

Benefits of VLANs

  • Improved security

  • Better performance

  • Smaller broadcast domains

  • Reduced costs

  • Increased IT efficiency

  • Enhanced management efficiency

Types of VLANs

  • Default VLAN (also known as VLAN 1): All switch ports are members of VLAN 1 by default.

  • Data VLAN: Created for specific user groups or devices, carrying user-generated traffic.

  • Native VLAN: Carries untagged traffic, default is VLAN 1.

  • Management VLAN: Created for network management traffic, typically VLAN 1.

VLAN Assignment Example

  • Assigning a VLAN ID:

    S1#configure terminal
S1(config)# vlan [vlan-id]
S1(config-vlan) name [vlan-name]
S1(config-vlan) end

  • Assigning Ports to VLANs:
    S1#configure terminal S1(config)# interface [interface-id] S1(config-if)# switchport mode access S1(config-if)# switchport access [vlan-id] S1(config-if)# end

Inter-VLAN Routing Operation

Definition

  • Inter-VLAN Routing: The process for forwarding network traffic from one VLAN to another using a router.

Methods of Inter-VLAN Routing

  1. Legacy Inter-VLAN Routing

  2. Router-on-a-Stick: Uses a router’s single physical interface configured as an 802.1Q trunk port.

  3. Layer 3 Switching using SVIs: Switch virtual interfaces are used to route traffic.

Router-on-a-Stick Configuration Example

  • Create a trunk link

  • Configure subinterfaces for each VLAN:
    R1(config)# interface g0/0.10 R1(config-subif)# encapsulation dot1Q 10 R1(config-subif)# ip address 172.17.10.1 255.255.255.0

  • Enable the physical interface:
    R1(config)# interface g0/0 R1(config-if)# no shutdown

DHCP Operation

Overview

  • Dynamic Host Configuration Protocol (DHCP): Automates assignment of IP addresses and other networking parameters.

  • Two types of addressing: Dynamic (DHCP-managed) and Static (manual entry).

DHCP Message Flow

  1. DHCPDISCOVER: Client broadcasts to find DHCP servers.

  2. DHCPOFFER: Server offers a lease to the client.

  3. DHCPREQUEST: Client requests the specific lease.

  4. DHCPACK: Server confirms the lease.

  5. DHCPNAK: If the offer is invalid, this message is sent, prompting a new discovery.