Networking Basics Every Cloud Engineer Should Know

Why Networking Matters in the Cloud

You can be great at writing code or managing servers, but if you don't understand networking, you'll hit walls constantly. Why can't my application reach the database? Why is this timing out?

Usually, it's networking.

IP Addresses: Your Cloud Address System

An IPv4 address looks like 192.168.1.100 - four numbers (0-255), separated by dots.

Private IP ranges (used inside your network):

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

Public IP addresses: Everything else. These are routable on the internet.

Subnets and CIDR

10.0.0.0/16 - What does this mean?

The /16 tells you how many bits are fixed:

/16 = first 16 bits fixed = 65,536 addresses
/24 = first 24 bits fixed = 256 addresses
/28 = first 28 bits fixed = 16 addresses

Practical Example

VPC: 10.0.0.0/16 (65,536 addresses)
├── Public Subnet: 10.0.1.0/24
├── Private Subnet A: 10.0.10.0/24
├── Private Subnet B: 10.0.11.0/24
└── Database Subnet: 10.0.20.0/24

Each subnet gets its own range. They can't overlap.

DNS: Translating Names to Numbers

Nobody wants to remember 54.231.17.108. We use names like www.example.com instead.

Common Record Types

A: Maps name to IPv4
AAAA: Maps name to IPv6
CNAME: Alias to another name
MX: Mail server
TXT: Text data

Private DNS

Inside your cloud network, use private DNS:

database.internal → 10.0.20.15

Your application connects to database.internal instead of an IP. If the database moves, just update DNS.

Load Balancing

When one server isn't enough, distribute traffic between multiple servers.

Types

Layer 4 (TCP): Routes based on IP and port. Faster.

Layer 7 (HTTP): Routes based on URL, headers. More flexible.

Cloud Load Balancers

Cloud	L4	L7
AWS	NLB	ALB
Azure	Load Balancer	Application Gateway
GCP	Network LB	HTTP(S) LB

VPNs and Private Connectivity

Site-to-Site VPN

Connects your office network to your cloud VPC through an encrypted tunnel.

Point-to-Site VPN

Individual users connect to cloud from anywhere.

Direct Connect/ExpressRoute

Dedicated physical connection. More bandwidth, more consistent, more expensive.

Troubleshooting Basics

When things don't connect, check:

Security Groups / Firewalls: Is the port allowed?
Route Tables: Is there a path to the destination?
DNS Resolution: Can you resolve the name?
Network ACLs: Stateless rules for entire subnets

Cheat Sheet

Common Ports:

22: SSH
80: HTTP
443: HTTPS
3306: MySQL
5432: PostgreSQL
6379: Redis

CIDR Quick Math:

/24 = 256 IPs
/25 = 128 IPs
/26 = 64 IPs
/27 = 32 IPs
/28 = 16 IPs

Networking isn't magic. It's just rules about how data moves from A to B. Learn the rules, and you'll solve problems much faster.