TOPIC #4Beginner 7 min read

IP Addressing (IPv4/IPv6, Public vs Private)

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Core Architecture Summary

Explore numerical addressing schemes, subnetting (CIDR), NAT (Network Address Translation), and why private VPCs shield internal architectures.

Key Glossary Concepts in this TopicAll Glossary Terms

Public Internet vs Private VPC Subnet 🛡️

How NAT Gateways allow private instances to access the internet without exposing their private IP addresses.

Public Internet vs Private VPC Subnet 🛡️

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01.1. IPv4 vs IPv6 Fundamentals

IPv4: 32-bit address space yielding ≈ 4.3 × 10^9 unique addresses (e.g. 192.0.2.1). Addresses are virtually exhausted worldwide.
IPv6: 128-bit address space yielding 3.4 × 10^{38} addresses (e.g. 2001:0db8:85a3:0000:0000:8a2e:0370:7334), eliminating address scarcity and reducing the need for NAT.

02.2. Public vs Private IP Spaces (RFC 1918)

Private IP ranges are reserved strictly for local networks and VPCs and are never routable over the public internet:

10.0.0.0 to 10.255.255.255 (10.0.0.0/8)
172.16.0.0 to 172.31.255.255 (172.16.0.0/12)
192.168.0.0 to 192.168.255.255 (192.168.0.0/16)

03.3. CIDR Notation & Subnet Calculations

Classless Inter-Domain Routing (CIDR) defines network masks. A /24 prefix leaves 32 - 24 = 8 host bits, creating 2^8 = 256 IPs (with 5 IPs typically reserved by cloud providers like AWS).

bash— Subnet breakdown for 10.0.1.0/24

# Network Address: 10.0.1.0
# Usable Range:    10.0.1.4 - 10.0.1.254 (in AWS VPC)
# Broadcast IP:    10.0.1.255
# Total addresses: 256

⚖️Architectural Trade-offs & Production Realities

Architectural Advantages

Private subnets block 100% of direct internet-borne attacks against databases

Trade-offs & Constraints

Requires NAT gateways and bastion hosts for egress/maintenance

Production Implementation in Big Tech

Amazon Web Services (AWS)• VPC Isolation

RDS databases are placed in isolated database subnets with no route table entry to an Internet Gateway, accessible solely via security groups linked to application compute clusters.

🎯 Staff+ Engineering Takeaways

IPv4 is 32-bit; IPv6 is 128-bit.
RFC 1918 private IPs (10.x.x.x, 192.168.x.x) are never routed on the public internet.
Keep internal data stores in private subnets behind security groups.

Topic Knowledge Assessment 🧠

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How many total IP addresses are contained in a /28 CIDR block?

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