4G sim only has private IP address, VPN from working

Forum|Forum|2 years ago
January 16, 2024
6 replies
7418 views

I have been experimenting with different sim card vendors in a Fortigate 60F-3G/4G. I have been trying to establish a remote access VPN connection to fortigate over 4G. So far I have been able to create a VPN connection locally so I know I understand the process and how it should work. I have also managed to get this working when the Fortigate is connected to the internet on it's WAN1 interface. I noticed when I insert a sim card, unlike the WAN 1 interface, the sim card interface (WWAN) receives a private IP address.

I have tried:

Vodafone: APN wap.vodafone.co.uk

O2: APN payandgo.o2.co.uk

3: automatically assign APN

Vodaphone sim was a pay monthly, I tried with both pay monthly and pay as you go O2 sim and the 3 sim was pay as you go. On all sim's i can ping out to the internet from the Fortigate just fine.

I've also tried using DDNS (use public IP) with no joy. Any help is greatly appreciated!

FortiGate

AEK

SuperUser

If I understand well, such sim is good for client applications (web browsing and so) but not for server apps, since your provider gives you a private address, so I guess it is not suitable for VPN server.

AEK

adambomb1219

SuperUser

Almost all cellular carriers use CG-NAT. You will need to request your provider to give you a public IP directly to your SIM Card.
What do you need inbound for on the cellular interface? Cellular failover is not typically a solution for inbound public connectivity.

ABE_63Author

New Member

Provider has said I need an IOT sim. Not entirely sure what the difference is but I'm guessing it's one that has a publicly assigned IP as opposed to CG-NAT.

Inbound on cellular is so i can make a secure connection to a moving vehicle when out of WiFi range.

adambomb1219

SuperUser

Yeah only your provider can answer these questions. But why not then build an outbound IPSec tunnel then?

Toshi_Esumi

SuperUser

I don't know UK situations. But in the US, we can get routable static IP services with separate APNs at least from "big three" carriers (VZW, AT&T, T-Mobile). You need to pay extra monthly in addition you might need to have a business account with them (cost a chuck at the beginning).
I would try ask your carrier if that's an option.

Toshi

Jonasanas

New Member

It sounds like you're running into a bit of a headache with that 4G SIM having a private IP address, which is why your VPN isn't working. It's not an uncommon issue, actually. Some mobile networks use private IPs to block direct access from the public internet, which messes with things like VPNs. One way around this could be using a temp mobile number to sign up for a different service that gives you a public IP. That should help you bypass the block. I’d also recommend trying to reset the connection or checking with your provider if they can give you a different setup for your IP.

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