What is CGNAT (and how does it impact NBN)?

NBN plans are built to just work. That means most Aussies won’t have issues with popular online tasks like browsing, emailing, social media, streaming and gaming. But there is, unfortunately, the possibility you might be encountering an invisible barrier if you’re seeking to perform more technical tasks like hosting a game server or access content from a NAS (like a Plex media server) remotely.

Let’s dig into what’s going on, how to solve it and which are the best NBN providers to consider if you want to avoid this issue. But before we get into all of that, here are the most popular NBN plans today.

CGNAT is short for ‘carrier-grade network address translation’. This clunky acronym gets in the way of server hosting on home internet connections because it effectively blocks port forwarding. Port forwarding is handy for manually providing access to certain online services. CGNAT is a stopgap solution to the finite number of IPv4 addresses that internet providers use to assign your home internet connection with an IP address. The long-term solution is IPv6, but that’s still not widely available.

Effectively, a once-exclusive home IP address is now shared across internet connections for multiple homes, which is why any online tasks that require port forwarding will fail if your provider is using CGNAT for your internet connection. For me personally, it meant I was unable to host a dedicated gaming server for Sons of the Forest (which would be true of any other games, too), and remote access for my Plex server always frustratingly failed. Thankfully, the solution for anyone who encounters this issue is as straightforward as choosing the right internet provider: either one that doesn’t use CGNAT at all, or one that makes it easy to opt out of the network blockage.

Note that if your NBN plan has a static IP address—either included or one you pay extra per month for—or your NBN provider uses IPv6, CGNAT won’t impact you. Additionally, Optus 4G Home and 5G Home users have CGNAT internet connections, which they can’t opt out of, and the same is true of Starlink plans.

The main disclaimer here is the following NBN providers may enable CGNAT in the future for customers if their IPv4 address allocation runs out (unless they shift to IPv6). Disclaimers aside, there are a handful of NBN providers we track in our comparison engine that don’t use CGNAT, including iiNet, More, Optus and TPG.

Here’s a daily snapshot of popular NBN plans from these CGNAT-free NBN providers.

There are several NBN providers in our database that have CGNAT enabled by default, but customers just need to contact them and ask to disable the feature. Best bit: there’s no extra charge for most of them. While Spintel has a $5 monthly fee to ditch CGNAT, the rest of these opt-out CGNAT NBN providers are reportedly free:

• AGL
• Aussie Broadband
• Dodo
• Exetel
• iPrimus
• Moose NBN
• Origin Broadband
• Southern Phone
• Superloop
• Swoop Broadband
• Tangerine
• Telstra

Check out the list of popular NBN plans from these opt-out CGNAT providers below.

In terms of the NBN providers we track in our comparison engine, there were still a few leftovers where their CGNAT status was murkier, except for Buddy Telco. Buddy has CGNAT, and there’s no way for customers to opt out. Belong uses CGNAT, but there was no clear information on whether customers can opt out. Kogan Internet, Mate, SkyMesh and Vodafone weren’t transparent on whether CGNAT is used at all.

If you’re not likely to need port forwarding, here’s a list of popular NBN plans from those providers.