C227 Computer System Technologies Lesson 10: Building a Simple Network

Building a Simple Network

• In a Simple Office Home Office (SOHO) setup, a network is required for resource sharing and internet access.
• Components required for a network include:
  • Computers
  • Internet Service Provider (ISP) equipment
  • Wireless router
  • Ethernet switch
  • Laptops
  • Ethernet cables
• Demo: Connecting devices in a home network using Packet Tracer

IPv4 Address Structure

• IPv4 addresses are 32-bit hierarchical addresses consisting of a network portion and a host portion
• A subnet mask is used to determine the network and host portions
• IPv4 addresses have 4 octets, with each octet made up of 8 bits
• A decimal of 255 is equivalent to 11111111 in binary

Subnet Mask

• A subnet mask is used to identify the network and host portions of an IPv4 address
• The subnet mask is compared to the IPv4 address bit by bit, from left to right, to identify the network and host portions
• The process of identifying the network and host portions is called ANDing

Prefix Length

• A prefix length is a less cumbersome method used to identify a subnet mask
• The prefix length is the number of bits set to 1 in the subnet mask
• It is written in "slash notation" (e.g., /8, /16, /24)

Network, Host, and Broadcast Addresses

• Within each network, there are three types of IP addresses:
  • Network address
  • Host addresses
  • Broadcast address
• The range of host addresses refers to the number of hosts that can be in a given network

Identifying Hosts on the Same Network

• To identify if two hosts are on the same network, AND the IP addresses with the subnet mask
• If the result is the same, the hosts are on the same network

IPv4 Unicast, Broadcast, and Multicast

• Unicast transmission is sending a packet to one destination IP address
• Multicast transmission is sending a packet to a multicast address group
• Broadcast transmission is sending a packet to every host on the network

Using the Subnet Calculator

• The subnet calculator can be used to determine the subnet mask, network address, broadcast address, first host IP address, and last host IP address

Types of IPv4 Addresses

• Public and private IPv4 addresses:
  • Public addresses are globally routed between ISP routers
  • Private addresses are used internally within a network and are not globally routable
• Special use IPv4 addresses:
  • Loopback addresses (127.0.0.0/8)
  • Link-Local addresses (169.254.0.0/16)
• Legacy classful addressing:
  • Class A (0.0.0.0/8 to 127.0.0.0/8)
  • Class B (128.0.0.0/16 to 191.255.0.0/16)
  • Class C (192.0.0.0/24 to 223.255.255.0/24)

Network Segmentation

• Broadcast domains and segmentation:
  • Switches propagate broadcasts out all interfaces except the interface on which it was received
  • Routers do not propagate broadcasts
• Problems with large broadcast domains:
  • Excessive broadcasts can negatively affect the network
• Reasons for segmenting networks:
  • Reduces overall network traffic and improves network performance
  • Can be used to implement security policies between subnets
  • Reduces the number of devices affected by abnormal broadcast traffic

Subnetting the Network

• Subnetting is the process of creating multiple logical networks that exist within a single class A, B, or C network

• Subnetting reduces overall network traffic and improves network performance

• Subnetting can be used to implement security policies between subnets

• Subnetting reduces the number of devices affected by abnormal broadcast traffic### Subnet Addressing

• A subnet address can be divided into 256 possible subnets, with 65,534 possible hosts per subnet, and a broadcast address.

• Each subnet has a unique subnet address, host range, and broadcast address.

Subnetting within an Octet Boundary

• Subnetting within an octet boundary means that the subnet mask falls on a natural boundary (e.g., /16, /24, etc.).
• However, subnetting does not have to be on an octet boundary; it can be done within a subnet mask that is not a power of 2 (e.g., /25, /26, etc.).

Subnet Masks in Binary

• A subnet mask can be represented in binary form, where n represents the network part and h represents the host part.
• Examples of subnet masks in binary form:
  • /25: 255.255.255.128, 11111111.11111111.11111111.10000000
  • /26: 255.255.255.192, 11111111.11111111.11111111.11000000
  • /27: 255.255.255.224, 11111111.11111111.11111111.11100000
  • /28: 255.255.255.240, 11111111.11111111.11111111.11110000
  • /29: 255.255.255.248, 11111111.11111111.11111111.11111000
  • /30: 255.255.255.252, 11111111.11111111.11111111.11111100

Subnet Calculator

• The subnet calculator can be used to determine the subnet address, first host address, last host address, and broadcast address of a subnet.
• Examples of using the subnet calculator:
  • Given an IP address of 10.96.255.4/20, the subnet calculator can determine that it belongs to the same network as the host 10.96.240.10/20.
  • Given an IP address of 192.16.0.0/24, the subnet calculator can subnet it into 4 subnets, with each subnet having a unique network address, first host address, last host address, and broadcast address.

Variable Length Subnet Masks (VLSM)

• VLSM allows a network space to be divided into unequal parts.
• With VLSM, the subnet mask will vary depending on how many bits have been borrowed for a particular subnet.
• VLSM is useful for dividing a network space into smaller subnets with different numbers of hosts.

This quiz covers the lesson on building a simple network, including IPv4 addressing, IP subnetting, and team activities from the C227 Computer System Technologies course.