Network Segmentation

Broadcast Domain

area in a LAN where broadcasts/ARP requests are propagated

ARP Purpose

discovers MAC addresses for known IPv4 addresses using Layer 2 broadcasts

DHCP Broadcasts

hosts send broadcasts to locate a DHCP server for IP configuration

Switch Broadcast Behavior

forwards broadcasts out all interfaces except the one received on

Routers and Broadcasts

routers do not forward broadcasts across interfaces

Router Interface Role

each router interface forms its own broadcast domain

Large Broadcast Domain Issue

too many hosts generate excessive broadcasts, slowing the network

Subnetting Purpose

reduces broadcast domain size to improve performance

Subnet Example

a /16 network split into /24 networks creates smaller broadcast domains

Subnetting Concept

uses host bits to create more networks with longer prefix lengths

Subnet vs Network

terms are interchangeable; most networks are subnets of larger blocks

Segmentation Benefit 1

reduces overall network traffic

Segmentation Benefit 2

allows administrators to enforce security policies between subnets

Segmentation Benefit 3

limits devices affected by abnormal or malicious broadcast traffic

Subnetting by Location

grouping devices geographically into separate subnets

Subnetting by Group/Function

separating departments or functions using different subnets

Subnetting by Device Type

placing device categories (e.g., printers, VoIP, servers) into unique subnets

Subnetting Skill Importance

fundamental skill for network administrators to manage and scale networks