NAT vs CGNAT: Understanding Network Address Translation
Master the differences between NAT and CGNAT. Learn how network address translation works, why ISPs use CGNAT, the impact on hosting servers and gaming, detection methods, and workarounds for common CGNAT limitations. Essential knowledge for understanding your network.
Quick Comparison
Regular NAT (Home Router)
Your home router performs NAT to share one public IP among all your devices.
- ✓Port forwarding works
- ✓Can host servers
- ✓P2P connections work
- ✓Full control over your router
CGNAT (ISP Level)
ISP adds another layer of NAT, sharing one public IP among multiple customers.
- ✗Port forwarding blocked
- ✗Cannot host servers
- ⚠P2P may be limited
- ✗No control over ISP NAT
How NAT Works
Network Address Translation (NAT) allows multiple devices with private IP addresses to share a single public IP address. Your home router is a NAT device.
NAT Translation Process
(Private IP)
(Public IP)
How CGNAT Works (Double NAT)
Carrier-Grade NAT (CGNAT), also called NAT444 or LSN (Large Scale NAT), adds a second layer of NAT at the ISP level. This means your traffic goes through TWO NAT devices.
CGNAT Translation Process
(NAT #1)
(NAT #2)
Why ISPs Use CGNAT
IPv4 Address Exhaustion
The primary reason is IPv4 address shortage. With only ~4.3 billion addresses and 5+ billion internet users, there aren't enough to go around.
- •IPv4 addresses are expensive to buy
- •CGNAT lets one IP serve 10-1000+ customers
- •Reduces ISP infrastructure costs
Common CGNAT Scenarios
- •Mobile networks: 4G/5G data connections
- •Budget ISPs: Low-cost internet providers
- •Student housing: Apartment complex networks
- •Rural ISPs: Limited infrastructure areas
- •New ISPs: Can't afford IPv4 blocks
What CGNAT Breaks
Services That Don't Work
Completely Broken
- ✗Hosting game servers (Minecraft, etc.)
- ✗Running web servers
- ✗Self-hosting services (Plex, etc.)
- ✗VPN servers (OpenVPN, WireGuard)
- ✗Remote desktop from internet
- ✗Port forwarding entirely
May Have Issues
- ⚠P2P file sharing (BitTorrent)
- ⚠Online gaming (NAT type issues)
- ⚠Video calling quality
- ⚠Some VoIP services
- ⚠IoT device remote access
- ⚠Some multiplayer games
How to Detect CGNAT
Method 1: Compare IP Addresses
- 1.Check your router's WAN IP: Log into your router and find the WAN/Internet IP address
- 2.Check your public IP: Visit LatencyLens or similar service
- 3.Compare them:
- • Same? No CGNAT ✓
- • Different? You're behind CGNAT ✗
- • WAN IP starts with 100.64-100.127? Definitely CGNAT ✗
Method 2: Port Forward Test
Try setting up port forwarding on your router. If it doesn't work even with correct configuration, you're likely behind CGNAT. Test with an online port checker tool.
Solutions and Workarounds
1. Request a Public IP from ISP
Some ISPs offer public (non-CGNAT) IPs for an additional fee (typically $5-20/month). Call and ask for a "public IP address" or "removal from CGNAT".
2. Use IPv6
IPv6 doesn't need NAT - every device gets a public address. Check if your ISP offers IPv6 and enable it on your router.
3. Use Cloud Services / Tunnels
- •Cloudflare Tunnel: Free tunnel for web services
- •ngrok: Expose local servers to internet
- •Tailscale/ZeroTier: Mesh VPN networks
- •PlayIt.gg: Game server tunneling
4. Get a VPS
Rent a cheap cloud server ($5-10/month) with a public IP and use it as a tunnel/proxy endpoint. Run your services there or tunnel traffic through it.
5. Switch ISPs
If possible, switch to an ISP that provides real public IPs. Business plans often include public IPs by default.