2.5 & 2.6: SOHO Networks and Network Configuration

IPv4 Addressing

Internet Protocol version 4; primary Layer 3 protocol used on most networks; uses 32-bit addresses written in dotted decimal.

IPv6 Addressing

Internet Protocol version 6; uses 128-bit addresses; provides 340 undecillion possible IPs; supported by all major OSs.

IPv4 Address Format

4 octets (32 bits) in dotted decimal notation (e.g., 192.168.1.1); each octet can be a value from 0 to 255.

IPv6 Address Format

128-bit hexadecimal address; first 64 bits represent the network prefix, last 64 bits represent the host portion.

IPv6 Addressing Capacity

Offers enough IPs for every person on Earth to have billions; helps resolve IPv4 address exhaustion.

Subnet Mask

Used to determine the subnet of an IP address; not transmitted across the network; e.g., 255.255.255.0.

Default Gateway

IP address of the router used to communicate outside of the local subnet; must be on the same subnet as the device.

DNS Server

Resolves domain names into IP addresses and vice versa; two DNS servers are commonly configured for redundancy.

DHCP

Dynamic Host Configuration Protocol; automatically assigns IP addresses, subnet mask, gateway, and other settings.

BOOTP

Bootstrap Protocol; an early protocol (1993) that partially automated IP addressing but required some manual configuration.

DHCP Process

Four-step process: Discover, Offer, Request, Acknowledge (DORA); used to dynamically assign IP addresses.

DHCP Static IP Option

You can disable DHCP and manually assign IPs; not recommended due to admin overhead.

DHCP Reservation

Preferred method to assign static IP; binds MAC address to IP address in DHCP server config.

APIPA

Automatic Private IP Addressing; used when DHCP fails; assigns an IP from 169.254.0.0/16; cannot communicate beyond local network.

Link-local Address

IP address usable only within a local subnet; APIPA provides link-local addresses for IPv4.

ARP with APIPA

Address Resolution Protocol is used to ensure the APIPA-assigned IP is not already in use by another device.

DNS

Translates human-readable names into computer-readable IP addresses; hierarchical and distributed.

DNS Root Servers

13 root server clusters (over 1000 actual servers); foundation of global DNS resolution.

gTLDs

Generic Top-Level Domains like .com, .org, .net, managed globally.

ccTLDs

Country Code Top-Level Domains like .us, .ca, .uk.

DNS Records (RR)

Resource records that store data like IP addresses, aliases, and certificates.

A Record

IPv4 address record; maps hostname to IPv4 address.

AAAA Record

IPv6 address record; maps hostname to IPv6 address.

MX Record

Mail Exchanger record; specifies mail server for a domain by hostname.

TXT Record

Holds human-readable text; used for verification and public info.

SPF Record

Sender Policy Framework; lists authorized mail servers for domain.

SPF Purpose

Helps prevent mail spoofing by verifying sending server.

DKIM

DomainKeys Identified Mail; digitally signs outbound email with public key in DNS.

DKIM Purpose

Validates authenticity of sender; adds email security.

DMARC

Domain-based Message Authentication, Reporting, and Conformance; works with SPF and DKIM.

DMARC Policy

Specifies what receiving servers should do with failed messages (accept, spam, reject).

DHCP Scope

Range of IP addresses a DHCP server can assign; includes subnet mask, lease duration, etc.

DHCP Pool

Group of IP addresses within a subnet; one scope per subnet.

DHCP Dynamic Assignment

Assigns available IP from pool; reclaims after lease expires.

DHCP Automatic Assignment

Keeps record of prior IPs; assigns same IP to returning device.

DHCP Reservation

Statically assigns IP to device based on MAC address.

Static DHCP Assignment

Alternative name for DHCP reservation; ensures consistent IP for a device.

DHCP Lease

Temporary IP address assignment; controlled by lease duration.

DHCP Reallocation

Lease is confirmed or reassigned upon reboot or request.

DHCP Release

Manually release IP address (e.g., when switching subnets).

DHCP T1 Timer

Renews IP lease with original DHCP server at 50% of lease duration.

DHCP T2 Timer

Rebinds IP with any DHCP server at 87.5% of lease duration.

LAN

Local Area Network; group of devices in same physical or broadcast domain.

VLAN

Virtual LAN; logically separates broadcast domains on same physical hardware.

VLAN Configuration

Assigns ports or devices to virtual LANs based on needs.

VPN

Virtual Private Network; encrypts data over public networks.

VPN Concentrator

Device or service handling encryption/decryption for VPN.

Client-to-Site VPN

Remote access to private network via VPN software; connects to concentrator.

Always-On VPN

VPN connection that stays enabled continuously for secure access.