CGNAT Explained: Why Port Forwarding Fails

Direct answer

CGNAT (carrier-grade NAT) puts many homes behind a shared public IP, so inbound port forwarding to your PC usually fails no matter how carefully you set the router. If friends cannot join your home-hosted world, hosting on GlassHosting moves the authoritative server off your ISP’s shared path onto a datacenter endpoint you share from the panel.

Symptoms / use case

Port forward “succeeds” in the router UI but friends still time out.
UPnP toggles change nothing for remote players.
You only get a private WAN address on the modem (100.64.0.0/10 or similar CGNAT space is a clue).
It works on LAN / same Wi-Fi but never from outside.

Practical explanation

Classic port forwarding assumes your home router has a dedicated public IPv4 address and can map inbound traffic to your PC. Under CGNAT, the carrier shares one public address across customers. Your router’s forward never becomes a globally reachable mapping. VPNs, “game boosters,” and random third-party relay apps are not a substitute for a proper hosted endpoint, and many violate game or host AUP if misused.

What to do instead

Stop burning evenings on forward folklore if you have confirmed CGNAT or apartment networking limits.
Order the game on GlassHosting from the billing catalog; provision after payment.
Open panel.glasshosting.com, copy the exact join IP/port shown for that server.
Migrate the world via SFTP/backup if you already have progress (see when to leave home PC hosting).
Test one remote friend before announcing to everyone.

Common mistakes

Buying a new router to “fix CGNAT” (hardware cannot create a public IP the carrier did not give you).
Exposing admin panels or RDP to the internet as a workaround.
Sharing your home IP after moving to hosted. Players should use the panel endpoint.

GlassHosting-specific workflow

Once hosted, you should not open living-room ports for that world. Join info comes from the panel; backups and restarts live there too. KB: Router and CGNAT issues. Category context: Home Server Setups.

How to confirm CGNAT without a networking degree

Check the WAN/IPv4 address your router shows.
Compare it to what a “what is my IP” site shows from a device on that LAN.
If they differ, or your WAN sits in shared carrier space, inbound forwards are not yours to give.
Optional: ask the ISP support chat whether you are on CGNAT or can purchase a public IPv4 (many residential plans will not).

Even with a public IP, residential upload and ToS can still make home hosting fragile. GlassHosting is the boring fix: authoritative server in the datacenter, players use the panel join string, you keep playing as a client.

What we will not recommend

Exposing RDP/SSH from home “so friends can manage the box.”
Untrusted relay tools that ask for game credentials.
Double-NAT laundry lists that still cannot create a public mapping.