// networking

What Is an IP Address?

An IP address is a numerical address used to identify and communicate with devices and services across an IP network, including the internet.

// definition

IP stands for Internet Protocol

An IP address is an address assigned to a network interface using the Internet Protocol. It allows data to be addressed and routed between devices across networks.

// basic idea

Think of it as a network address

When data travels across a network, computers need to know where it should be sent.

Your device | v Network | v IP address | v Destination device or server

The Internet Protocol uses IP addresses as part of this addressing and routing process.

// IPv4

What does an IPv4 address look like?

One common type of IP address is an IPv4 address.

It is written as four decimal numbers separated by dots.

192.168.1.25

Each section represents 8 bits and can range from 0 to 255.

192 . 168 . 1 . 25 | | | | 8 bits 8 bits 8 bits 8 bits

IPv4 addresses are therefore 32 bits long.

4 x 8 bits = 32 bits

// address space

How many IPv4 addresses are possible?

A 32-bit address provides:

2^32 = 4,294,967,296

That is approximately 4.3 billion possible IPv4 addresses.

Not all of those addresses are available as ordinary public internet addresses because portions of the address space are reserved for particular purposes.

// IPv6

What is IPv6?

The newer version of Internet Protocol addressing is IPv6.

IPv6 addresses are 128 bits long and are normally written in hexadecimal.

2001:0db8:85a3:0000:0000:8a2e:0370:7334

IPv6 provides a vastly larger address space than IPv4.

IPv4 = 32 bits IPv6 = 128 bits

// comparison

IPv4 vs IPv6

IPv4

32-bit addresses written using four decimal numbers separated by dots.

IPv6

128-bit addresses normally written using hexadecimal groups separated by colons.

// public IP

What is a public IP address?

A public IP address is an address used for communication across the public internet.

For example, a home router may have a public IP address assigned by an internet service provider.

Internet | v Public IP address | v Router | v Local network

Public IP addresses must be globally routable and cannot simply be duplicated arbitrarily across the public internet.

// private IP

What is a private IP address?

Devices inside homes and businesses commonly use private IP addresses.

Common IPv4 private address ranges include:

10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255.255

These addresses can be reused on different private networks because they are not routed directly across the public internet.

// NAT

How can many devices share one public IP address?

Home and business networks commonly use Network Address Translation, or NAT.

Laptop 192.168.1.10 Phone 192.168.1.11 TV 192.168.1.12 | v Router | v One public IP address | v Internet

NAT allows multiple devices using private addresses to communicate through a smaller number of public IP addresses.

// assignment

Static vs dynamic IP addresses

Static IP

An address intended to remain fixed unless it is deliberately changed.

Dynamic IP

An address that may be assigned automatically and can change over time.

Internet service providers often assign dynamic public IP addresses to residential customers, while servers and business services may use static addressing where a stable address is useful.

// DHCP

How do devices get an IP address?

On many local networks, IP addresses are assigned automatically using:

DHCP Dynamic Host Configuration Protocol

A DHCP server can provide devices with information such as an IP address, subnet configuration, default gateway and DNS servers.

// DNS

IP addresses and domain names

Humans generally prefer names such as:

example.com

Computers communicating over IP networks ultimately use network addresses.

DNS helps connect these ideas.

Domain name | v DNS | v IP address | v Server

For example, an A record can map a hostname to an IPv4 address, while an AAAA record can map a hostname to an IPv6 address.

// URL

An IP address is not a URL

Consider:

https://example.com/products/item

This is a URL.

The hostname:

example.com

can be resolved through DNS to an IP address.

The rest of the URL identifies the protocol and the resource being requested.

// routing

How IP addresses help route data

Data sent using Internet Protocol is divided into packets.

IP packets contain addressing information including source and destination IP addresses.

Source IP | v Packet | v Routers | v Destination IP

Routers examine network information and decide where packets should be forwarded next.

// subnet

What is a subnet?

IP networks can be divided into smaller networks called subnets.

You may see notation such as:

192.168.1.0/24

The /24 is CIDR notation. It indicates that the first 24 bits describe the network portion of the IPv4 address.

192.168.1.0/24 Network portion = first 24 bits Host portion = remaining 8 bits

// special addresses

What is 127.0.0.1?

The IPv4 address:

127.0.0.1

is a loopback address commonly associated with:

localhost

It refers back to the local computer rather than another device on the internet.

Developers often use localhost when testing applications on their own machine.

// web servers

Does every website have its own IP address?

Not necessarily.

Multiple websites can share the same server and the same public IP address.

Website A Website B Website C | v Shared web server | v 203.0.113.10

Modern web servers can determine which website is being requested from information such as the hostname supplied by the browser.

// location

Can an IP address reveal your exact location?

An IP address can sometimes provide approximate geographic information, such as a country, region or general area.

However, an IP address does not inherently contain a person's exact home address or precise physical location.

Important: IP geolocation databases are estimates. Their results can be inaccurate, and networks such as mobile networks, VPNs and corporate systems can make the apparent location very different from the user's actual location.

// changing addresses

Can your IP address change?

Yes.

A device may receive a different IP address when:

Network changes

Connecting to a different Wi-Fi or mobile network can give the device different addressing.

DHCP changes

A dynamically assigned address can change when its network lease changes.

ISP changes

An internet provider may assign a different public address over time.

VPN usage

Internet services may see the VPN server's public IP address rather than the user's ordinary public IP.

// mental model

The easiest way to remember it

Domain name = human-readable name DNS = translates names into network information IP address = network address Router = forwards packets between networks Server = provides a service URL = identifies a specific web resource

The IP address is therefore one of the fundamental pieces of information used to move data from one network location to another.

// summary

An IP address identifies a network destination.

An IP address is an address used by the Internet Protocol to identify network interfaces and route data. IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses. Devices may use public or private addresses, and DNS helps connect human-readable domain names to IP addresses.

// networking

What Is DNS?

DNS is the system that connects human-readable domain names to the servers and services behind them. Without DNS, using the web would usually require remembering numerical network addresses instead of names such as freelancecoder.uk.

// definition

DNS means Domain Name System

DNS, or the Domain Name System, is a distributed system used to translate domain names into information that computers can use to locate internet services.

// basic idea

Domain name to server

People prefer names. Computers ultimately need network addresses and routing information.

Domain name | v DNS lookup | v IP address or another DNS destination | v Server | v Website or service

When you enter a domain into a browser, DNS helps determine where the request should be sent.

// example

A simple DNS lookup

Imagine that a browser needs to open:

www.example.com

The browser needs to determine which server or service is responsible for that hostname.

www.example.com | v DNS | v Destination | v Web server

Once the destination has been found, the browser can begin communicating with the appropriate server.

// distinction

Domain, DNS and hosting are different

Domain

The human-readable name, such as example.com.

DNS

The system that tells computers where services associated with that name can be found.

Hosting

The server or platform that stores and serves the website or application.

Website

The actual pages, files and application content that visitors interact with.

Domain | v DNS | v Hosting | v Website

// records

Common DNS record types

DNS stores different kinds of information in DNS records.

A

Maps a hostname to an IPv4 address.

AAAA

Maps a hostname to an IPv6 address.

CNAME

Makes one hostname an alias of another hostname.

MX

Identifies the mail servers responsible for receiving email for a domain.

TXT

Stores text information. TXT records are commonly used for domain verification and email-related policies.

NS

Identifies the authoritative nameservers responsible for a DNS zone.

// A record

Pointing a domain to an IPv4 address

An A record maps a hostname directly to an IPv4 address.

example.com | v A record | v 203.0.113.10

The exact IP address will depend on the server or hosting platform being used.

// CNAME

Pointing one hostname to another

A CNAME record creates an alias between hostnames.

www.example.com | v CNAME | v hosting.example.net

The DNS system can then continue resolving the destination hostname.

Important: a CNAME points to another hostname, not directly to an IP address.

// email

DNS also controls email routing

DNS is not only used for websites.

MX records tell other mail systems which servers should receive email for a domain.

person@example.com | v DNS MX lookup | v Mail server | v Mailbox system

This is why changing website hosting does not necessarily mean changing email hosting.

// nameservers

What are nameservers?

Nameservers are DNS servers responsible for providing information about domains and DNS zones.

A domain registrar may allow you to select which nameservers are authoritative for your domain.

Domain | v NS records | v Authoritative nameservers | v DNS records

Those authoritative servers contain or serve the DNS records that describe where the domain's services should go.

// hierarchy

DNS is hierarchical

Domain names are organised into levels.

www.example.com www = hostname / subdomain example = registered domain label com = top-level domain

At the very top of DNS is the DNS root.

DNS root | v .com | v example.com | v www.example.com

Terminology: people sometimes informally call example.com the "root domain", but in DNS terminology the actual DNS root is the top of the global DNS hierarchy.

// resolution

How DNS resolution works

A DNS lookup can involve several different systems.

Browser | v DNS resolver | v DNS hierarchy | v Authoritative nameserver | v DNS answer | v Browser

A recursive resolver performs or coordinates the lookup required to obtain the answer for the client.

// caching

DNS answers can be cached

DNS systems often cache previous answers so that every lookup does not have to repeat the full resolution process.

This improves speed and reduces unnecessary DNS traffic.

// TTL

What is TTL?

DNS records commonly include a value called TTL, meaning Time To Live.

TTL tells DNS caches approximately how long a record may be retained before it should be refreshed.

TTL = 3600 3600 seconds = 1 hour

A DNS change may therefore not appear everywhere immediately because some systems may still have an older answer cached.

// propagation

What does DNS propagation mean?

When people say that DNS is propagating, they usually mean that different DNS resolvers and caches are gradually replacing previously cached information with newer records.

Old DNS record | v DNS record changed | v Some caches still contain old answer | v Caches expire and refresh | v New answer becomes widely visible

The term "propagation" is convenient, although much of the delay is actually caused by caching and TTL behaviour.

// URL

DNS does not resolve an entire URL

Consider:

https://www.example.com/articles/dns

DNS is primarily concerned with the hostname:

www.example.com

The rest of the URL is handled by the web request and the server or application.

// IP

DNS and IP addresses

DNS and IP addresses solve different parts of the problem.

Concept	Purpose
Domain name	Human-readable name.
DNS	Resolves names and provides service information.
IP address	Network address used for routing traffic.
Server	Handles requests and provides a service.

// practical

When would you edit DNS?

You may need to change DNS records when:

Connecting a website

Pointing a domain to Blogger, WordPress, a hosting company or another web platform.

Configuring email

Adding MX and other email-related records.

Verifying ownership

Adding a TXT or CNAME record to prove control of a domain.

Creating subdomains

Connecting names such as blog.example.com or api.example.com to services.

// mental model

A useful way to remember DNS

Domain = name DNS = directions IP address = network address Hosting = where the service runs Website = what the visitor sees

DNS acts as the connection between the name people type and the internet service that should receive the request.

// summary

Names need directions.

DNS stands for Domain Name System. It connects domain names with the servers and services behind them using records such as A, AAAA, CNAME, MX, TXT and NS. DNS is separate from the domain itself, the hosting platform and the website content, but it is the system that connects those pieces together.

// websites

What Is Web Hosting?

Web hosting is the infrastructure that makes a website available on the internet. A hosting provider supplies the computing resources needed to store, run and serve website content to visitors.

// definition

Hosting is where a website runs

Web hosting is a service that provides server resources for websites and web applications.

These resources can include storage, processing power, memory, networking, databases and software.

When someone visits a website, the hosting system delivers the required content to their browser.

// simple model

A website needs somewhere to live

Website files ↓ Web hosting ↓ Internet ↓ Visitor's browser

Without hosting or some equivalent server infrastructure, the website files may exist on a computer but would not normally be publicly accessible to internet users.

// server

Hosting normally involves servers

A server is a computer or software system that responds to requests from other computers.

For a website, a web server may receive a request such as:

GET /about

It can then return the appropriate HTML, CSS, JavaScript, images or generated content.

// request

What happens when someone visits a website?

User enters domain ↓ DNS finds destination ↓ Browser connects to hosting server ↓ Browser requests page ↓ Server processes request ↓ Server returns content ↓ Browser renders website

This process can happen in a fraction of a second.

// domain vs hosting

A domain and hosting are different

A domain is the human-readable internet name.

Hosting is the infrastructure that serves the website.

freelancecoder.uk ↓ Domain name Web server / platform ↓ Hosting

You can buy a domain without buying hosting. You can also move a website to different hosting while keeping the same domain.

// important distinction

Hosting is not the website itself

Website

The pages, code, images, content and application logic.

Hosting

The infrastructure used to store or run that website.

Domain

The name people use to reach the website.

DNS

The system that connects the name to the service.

// static hosting

Some hosting simply serves files

A static website may consist primarily of:

index.html styles.css script.js logo.png

The hosting platform can send these files directly to visitors.

No server-side programming language necessarily needs to run for every page request.

// dynamic hosting

Dynamic websites can run application code

More complex hosting can execute code before producing the response.

Browser request ↓ Web server ↓ PHP / Python / Node.js ↓ Database ↓ Generated HTML or JSON ↓ Browser

This allows a website to generate different content depending on users, data and application logic.

// storage

Hosting provides storage

A website may need space for:

HTML CSS JavaScript Images Videos Documents Databases Backups

// resources

Hosting also provides computing resources

Resource	Purpose
CPU	Processes application instructions
RAM	Temporary working memory
Storage	Stores website files and data
Bandwidth	Transfers data across the network
Database	Stores structured application data

// shared hosting

What is shared hosting?

Shared hosting places multiple customers or websites on the same underlying server infrastructure.

Server │ ├── Website A ├── Website B ├── Website C └── Website D

Resources are shared between multiple hosted sites.

This can make shared hosting inexpensive and simple, although it normally offers less isolation and control than dedicated environments.

// vps

What is VPS hosting?

VPS stands for Virtual Private Server.

Virtualisation divides physical server resources into separate virtual environments.

Physical Server │ ├── VPS 1 ├── VPS 2 ├── VPS 3 └── VPS 4

A VPS generally gives the customer more control over the server environment than ordinary shared hosting.

// dedicated server

What is dedicated hosting?

Dedicated hosting gives one customer access to an entire physical server or dedicated hardware environment.

It can provide substantial control and predictable resources but is generally more expensive and requires greater technical management.

// cloud hosting

What is cloud hosting?

Cloud hosting uses computing resources provided through larger distributed cloud platforms.

Instead of thinking only in terms of one physical server, applications can use virtual machines, databases, object storage, load balancers, serverless functions and other cloud services.

Application │ ├── Compute ├── Database ├── Storage ├── CDN └── Networking

// managed hosting

Managed hosting reduces administration

With managed hosting, the provider handles more of the technical infrastructure.

Server Updates Security Backups Monitoring Performance

The exact level of management depends on the provider and hosting plan.

// hosted platforms

Some platforms include hosting automatically

Services such as blogging platforms and website builders often hide much of the hosting infrastructure from the user.

Create website ↓ Platform stores content ↓ Platform runs servers ↓ Platform serves website

The site owner can concentrate on the website while the platform manages most of the underlying hosting.

// blogger example

Blogger includes hosting

A Blogger site does not require you to rent and configure your own web server.

Google operates the hosting infrastructure while the site owner manages the posts, pages, template and domain configuration.

Custom domain ↓ DNS ↓ Blogger ↓ Google hosting infrastructure

// wordpress

WordPress can be hosted in different ways

WordPress software can run on many hosting providers.

A managed WordPress platform may handle most server administration automatically, while self-managed WordPress hosting can give the site owner much more control over the environment.

// web server software

Hosting may run web server software

Common web server technologies include:

Apache Nginx Caddy IIS

These systems can receive HTTP requests and return website content to users.

// database hosting

Dynamic websites often need a database

Website ↓ Application code ↓ Database

A hosting plan may provide databases such as MySQL or PostgreSQL, or the database may run on a completely separate service.

Smaller applications may also use file-based databases such as SQLite.

// https

Hosting often provides HTTPS support

Modern websites generally use HTTPS to encrypt communication between the website and its visitors.

Browser ⇅ Encrypted HTTPS connection ⇅ Hosting server

Many modern hosting platforms can automatically issue, install and renew SSL/TLS certificates after a domain has been connected correctly.

// bandwidth

Hosting transfers data to visitors

Every time someone loads a page, data travels from the hosting infrastructure to their device.

HTML CSS JavaScript Images Fonts Video API responses

This data transfer is commonly described in terms of bandwidth or traffic.

// cdn

A CDN can work alongside hosting

CDN stands for Content Delivery Network.

A CDN can cache copies of website resources on servers in multiple locations.

Origin hosting ↓ CDN network ↙ ↓ ↘ London Paris New York

Visitors may receive cached resources from infrastructure closer to them rather than retrieving everything directly from the origin server.

// uptime

Hosting affects website availability

If the hosting infrastructure becomes unavailable, visitors may be unable to reach the website even though the domain itself still exists.

Domain working + DNS working + Hosting unavailable ↓ Website unavailable

Domain registration and website availability are therefore separate issues.

// backups

Backups are an important part of hosting

Websites can contain code, images, databases, user content and configuration that may be difficult to recreate.

Good hosting arrangements should consider how that information can be backed up and restored.

// email

Website hosting and email hosting can be separate

A domain can send website traffic to one provider while email is handled by another.

example.com │ ├── Website │ → Web host │ └── Email → Mail provider

DNS records determine which services handle each type of traffic.

// self-hosting

You can technically host a website yourself

A computer connected to the internet can potentially run web server software and serve a website.

However, public hosting requires consideration of networking, security, reliability, backups, power, software updates and availability.

For this reason, most public websites use specialist hosting infrastructure.

// hosting types

Common hosting models

Type	Basic idea
Shared	Multiple websites share infrastructure
VPS	Virtual server environment
Dedicated	Dedicated server resources
Cloud	Resources delivered through cloud infrastructure
Managed	Provider handles more administration
Static	Primarily serves pre-built files

// mental model

The web stack becomes easier to understand

Domain ↓ DNS ↓ Hosting ↓ Web server / application ↓ HTML + CSS + JavaScript ↓ Browser

Each layer performs a different job.

// summary

The infrastructure behind the website.

Web hosting provides the server resources and network infrastructure needed to make websites available on the internet. The domain gives the website a name, DNS directs requests, and the hosting environment stores or runs the website and delivers its content to visitors.

// internet

What Is a Web Domain?

A web domain is the human-readable name used to identify a location on the internet. Instead of remembering a numerical IP address, people can enter a name such as freelancecoder.uk into a browser.

// definition

A domain is an internet name

A domain name is a name registered within the Domain Name System, or DNS.

It gives people and software a memorable way to refer to websites, servers, email services and other internet resources.

For example:

freelancecoder.uk

// why domains exist

Computers and humans identify things differently

Internet systems communicate using numerical network addresses such as IP addresses.

Humans generally find names easier to remember.

Human-friendly: freelancecoder.uk Machine address: 216.239.32.21

DNS provides the system that connects domain names to the technical resources behind them.

// dns

DNS connects domain names to internet services

DNS stands for Domain Name System.

When someone enters a domain into a browser, DNS can be used to determine where that request should be sent.

freelancecoder.uk ↓ DNS ↓ IP address or another hostname ↓ Web server ↓ Website

// structure

A domain has different parts

Consider:

freelancecoder.uk

freelancecoder

The registered name chosen for the domain.

.uk

The top-level domain at the end of the name.

// top-level domain

What is a TLD?

TLD stands for Top-Level Domain.

It is the final part of a domain name.

.com .uk .org .net .dev .io .info .xyz

// country domains

Some TLDs represent countries

Country-code top-level domains are known as ccTLDs.

TLD	Country or territory
.uk	United Kingdom
.pt	Portugal
.fr	France
.de	Germany
.es	Spain

// subdomains

A domain can have subdomains

Consider:

www.freelancecoder.uk

Here:

www ↓ subdomain freelancecoder.uk ↓ registered domain

Other examples could include:

blog.example.com shop.example.com api.example.com docs.example.com

Different subdomains can point to different services.

// root domain

What is the root or apex domain?

The domain without a subdomain is often called the apex domain or root domain.

freelancecoder.uk

By comparison:

www.freelancecoder.uk

contains the www subdomain.

// domain vs url

A domain is not the same as a URL

A domain might be:

freelancecoder.uk

A complete URL might be:

https://www.freelancecoder.uk/contact

The URL contains additional information.

Part	Example
Protocol	https://
Hostname	www.freelancecoder.uk
Domain	freelancecoder.uk
Path	/contact

// domain vs website

A domain is not the website itself

This is an important distinction.

Domain → the internet name Website → the pages, files and application Hosting → the infrastructure that serves the website

You can own a domain without having a website attached to it.

You can also move a website to another hosting provider while keeping the same domain name.

// registrar

Domains are registered through registrars

A domain registrar is a company authorised to register domain names for customers.

When a domain is available, you can register the right to use it for a particular registration period.

Choose domain ↓ Registrar ↓ Register domain ↓ Configure DNS ↓ Connect services

// registry

Registrars and registries are different

The registrar is normally the company through which the customer manages the registration.

The registry operates the database and infrastructure for a particular top-level domain.

Registrant ↓ Registrar ↓ Registry ↓ Domain Name System

// nameservers

Nameservers tell the internet where DNS records live

A domain is normally assigned authoritative nameservers.

These servers provide DNS information for the domain.

Domain ↓ Nameservers ↓ DNS records ↓ Website / Email / Other services

Changing nameservers can effectively move responsibility for managing the domain's DNS records to another provider.

// dns records

DNS records control where services point

Record	Common purpose
A	Points a name to an IPv4 address
AAAA	Points a name to an IPv6 address
CNAME	Aliases one hostname to another
MX	Directs email delivery
TXT	Stores text used for verification and policies
NS	Identifies authoritative nameservers

// a record

An A record can point a domain to a server

freelancecoder.uk ↓ A record ↓ 216.239.32.21

An A record maps a hostname to an IPv4 address.

// cname

A CNAME can point one name to another

www.freelancecoder.uk ↓ CNAME ↓ ghs.google.com

This allows the www hostname to reference another hostname instead of directly containing an IP address.

// email

Domains can also be used for email

A domain is not limited to websites.

The same domain could also support addresses such as:

hello@example.com support@example.com accounts@example.com

DNS records can direct email traffic to a mail provider independently of where the website is hosted.

// https

A domain can be protected with HTTPS

HTTPS encrypts communication between a browser and a website.

http://example.com ↓ https://example.com

HTTPS normally uses a digital certificate associated with the domain or hostname.

The domain and the SSL/TLS certificate are separate things. Registering a domain does not itself create the website, although many hosting platforms automatically provide HTTPS certificates after the domain is connected.

// dns changes

DNS changes may not appear everywhere immediately

DNS information is cached by resolvers and other systems.

When a record changes, some systems may continue using the older cached information until it expires.

Old DNS record ↓ Record changed ↓ Caches expire ↓ New record becomes widely visible

This process is commonly described as DNS propagation.

// ttl

DNS records have a TTL

TTL means Time To Live.

It tells DNS resolvers approximately how long a record may be cached before it should be refreshed.

TTL: 3600 3600 seconds = 1 hour

// registration

Domain registrations must normally be renewed

A domain is generally registered for a defined period.

To continue controlling the domain, the registration normally needs to be renewed before it ultimately expires.

Register ↓ Use domain ↓ Renew ↓ Continue using domain

// ownership

"Buying" a domain is really a registration right

People often say they have bought a domain.

More precisely, they have registered the right to use that domain according to the rules of the relevant registry and registrar for as long as the registration remains valid.

// transfers

Domains can usually be transferred

A domain can often be moved from one registrar to another without changing the domain name itself.

Registrar A ↓ Domain transfer ↓ Registrar B

The website can remain on the same hosting platform if the DNS configuration continues pointing to the same destination.

// one domain

One domain can connect many services

example.com │ ├── www.example.com │ → website │ ├── api.example.com │ → API │ ├── shop.example.com │ → online store │ └── email@example.com → email service

DNS makes it possible for these services to be hosted in completely different places while sharing the same domain.

// domain + hosting

The domain and hosting can come from different companies

You do not normally have to register a domain with the same company that hosts the website.

Domain registrar ↓ DNS ↓ Website host

This separation is one of the most useful features of the Domain Name System.

// mental model

A simple way to think about domains

Domain

The memorable internet name.

DNS

The system that tells software where services are.

Hosting

The infrastructure that stores or runs the website.

HTTPS

The secure encrypted connection used to reach it.

// summary

A human-readable internet address.

A web domain is a registered name used to identify internet resources. DNS connects that name to websites, servers, email systems and other services. The domain, DNS, hosting and website are separate components that work together to make an internet service accessible.