IPv4

Networking

Internet Protocol version 4. Uses 32-bit addresses (e.g., 192.0.2.1), giving roughly 4.3 billion unique addresses. Address exhaustion forced widespread use of NAT, complicating CDN architectures and Anycast routing.

Updated Mar 9, 2026

Full Explanation

IPv4 has been the backbone of the internet since the early 1980s. Its 32-bit address space seemed enormous at the time but ran out of free allocations in 2011. Today, every CDN must work within a world of NAT (Network Address Translation), where thousands of users share a single public IP.

For CDNs, IPv4 matters in a few ways. Anycast routing—where the same IP is announced from multiple PoPs—relies on having IP address blocks at each location. IPv4 address blocks are expensive and scarce, which can limit how many Anycast IPs a CDN can deploy. NAT also complicates rate limiting and abuse detection since many legitimate users appear to come from the same IP.

Most CDNs run dual-stack (IPv4 + IPv6), but IPv4 remains necessary because a significant chunk of clients, especially on older networks, still only speak IPv4.

Examples

Checking which IP version your CDN connection uses:

# Force IPv4
curl -4 -sI https://cdn.example.com/ | head -5

# Check the resolved IP
dig A cdn.example.com +short
# 198.51.100.42

Nginx listening on IPv4 only vs dual-stack:

# IPv4 only
server {
    listen 80;
    listen 443 ssl;
}

# Dual-stack (IPv4 + IPv6)
server {
    listen 80;
    listen [::]:80;
    listen 443 ssl;
    listen [::]:443 ssl;
}

Video Explanation

Frequently Asked Questions

Internet Protocol version 4. Uses 32-bit addresses (e.g., 192.0.2.1), giving roughly 4.3 billion unique addresses. Address exhaustion forced widespread use of NAT, complicating CDN architectures and Anycast routing.

Checking which IP version your CDN connection uses:

# Force IPv4
curl -4 -sI https://cdn.example.com/ | head -5

# Check the resolved IP
dig A cdn.example.com +short
# 198.51.100.42

Nginx listening on IPv4 only vs dual-stack:

# IPv4 only
server {
    listen 80;
    listen 443 ssl;
}

# Dual-stack (IPv4 + IPv6)
server {
    listen 80;
    listen [::]:80;
    listen 443 ssl;
    listen [::]:443 ssl;
}

Related CDN concepts include:

  • IPv6 — Internet Protocol version 6. Uses 128-bit addresses (e.g., 2001:db8::1), providing a virtually unlimited address space. …
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