Someone asked me recently whether mobile proxies are "just CGNAT," like it was a gotcha. And yeah — they are. That's not the catch. That's the entire reason they work.

Let me unpack that, because "carrier-grade NAT" sounds like a downside until you see what it's actually doing for you.

What CGNAT is

There aren't enough IPv4 addresses for every device on earth to have its own. Mobile carriers solved this the obvious way: they put a lot of subscribers behind a smaller set of public IPs using carrier-grade NAT (the formal name is RFC 6598, and it uses the 100.64.0.0/10 range on the carrier side). Your phone thinks it has an address; out on the public internet, you're sharing one with a crowd.

Fixed-line ISPs increasingly do it too, but on mobile it's essentially universal. If you're on 4G or 5G right now, you're almost certainly behind CGNAT.

Why sharing an IP is a feature here

For a normal home server, CGNAT is annoying — you can't easily host anything because the IP isn't really "yours." But for staying un-blocked, sharing is exactly what you want.

Think about it from the website's side. It sees traffic from one mobile IP and has to decide: real person, or bot? Behind that single address are hundreds of genuine users — people checking Instagram, buying things, reading the news. If the site blocks that IP, it blocks all of them. That's a real cost, so sites are extremely reluctant to do it.

A dedicated datacenter IP has the opposite problem. It's yours alone, which sounds nice until you realise there's no crowd to hide in. One flagged action and the whole IP is burned, because banning it costs the site nothing.

So the shared, CGNAT nature of a mobile IP isn't a weakness you tolerate — it's the thing providing the cover.

How to check if an IP is behind CGNAT

You can't always tell from the public IP alone, but you can get a strong read. If an address falls inside 100.64.0.0/10 it's CGNAT by definition. Beyond that, the owning network tells you a lot: a mobile carrier ASN almost always means CGNAT. A quick CGNAT checker runs both checks for you, and the ASN lookup shows the carrier behind any IP if you want to confirm it's really a mobile network.

The catch worth knowing

Shared IPs do have one real tradeoff: you inherit your neighbours' behaviour a little. If the pool is stuffed with abuse, some of that reputation rubs off. This is why how a provider sources its IPs matters more than the headline "mobile" label. Real SIM cards on real carrier plans, shared with genuine traffic, stay clean. Recycled or abused ranges don't.

That's the difference between a mobile proxy that quietly works and one that's already half-burned when you get it — and it's why VeilSocks runs genuine carrier SIMs rather than whatever's cheapest. CGNAT gives you the crowd; clean sourcing makes sure it's a crowd you want to be standing in.