WiFi Calling Bypasses VPN

[sbsnb]

I run OpenVPN Connect on my Android phone, which connects to my RT-AC88U's VPN server 24x7. All seems to work as expected except WiFi calling. Somehow that is able to bypass the VPN and is directly connected to my cellular provider's network via whatever WiFi I'm connected to. I don't appreciate the privacy implications of random WiFi hotspots having the power to "see" my phone calls. I just can't figure out how it's bypassing the VPN. Any ideas appreciated.

 

[JDB]

Wi-fi calling is actually done over an IPsec tunnel to the carrier anyway so you are protected.


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[sbsnb]

The reason I discovered the problem is that my company WiFi blocks those ports (not because they intentionally want to block WiFi calling, but because they are clueless and just enable total port blocking on everything >1024 AND all UDP traffic), so WiFi calling doesn't work when I'm connected to their WiFi. My VPN still works fine, however. I would rather that the traffic were routed over the VPN.

 

[JDB]

There’s no way around it. The phone doesn’t allow it as it would be an easy way to allow Wi-fi calling when out of country, this is the primary reason it bypasses the VPN.


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[sbsnb]

I suppose if it's not possible, I can at least set up a rogue hot spot at work with a VPN tunnel to my RT-AC88U and connect to that instead of the official company WiFi.

 

[JDB]

I suppose if it's not possible, I can at least set up a rogue hot spot at work with a VPN tunnel to my RT-AC88U and connect to that instead of the official company WiFi.

Yep I’ve done exactly that before when I was abroad for 6 weeks to avoid roaming charges [emoji23]


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[L&LD]

I suppose if it's not possible, I can at least set up a rogue hot spot at work with a VPN tunnel to my RT-AC88U and connect to that instead of the official company WiFi.

Be careful that you'll get what you want with this method!

Have a VPN tunnel for your phone vs. having a job...

 

[martinr]

Be careful that you'll get what you want with this method!

Have a VPN tunnel for your phone vs. having a job...

Ah, L&LD, you’ve reminded me:

https://www.snbforums.com/threads/please-help-with-putty-to-asus-merlin-ssh.44559/#post-380488

 

[unsynaps]

I had no idea Android even had wifi calling.

But on android you can flat out force it?

 

[SMS786]

I had no idea Android even had wifi calling.

But on android you can flat out force it?

Yep, enable wifi calling (wifi preferred) and then turn on airplane mode, but keep the wifi radio on

 

[FreshJR]

There’s no way around it. The phone doesn’t allow it as it would be an easy way to allow Wi-fi calling when out of country, this is the primary reason it bypasses the VPN.


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Then have the router/laptop act as a VPN Client on behalf of the phone and problem solved

Just wanted to poke fun at that reason. I know my carrier zero rates WiFi calling but make sure airplane mode is on so it never hits cellular fallback .

 

[JDB]

Then have the router/laptop act as a VPN Client on behalf of the phone and problem solved

Just wanted to poke fun at that reason. I know my carrier zero rates WiFi calling but make sure airplane mode is on so it never hits cellular fallback .

It is the main reason, I work with many of the telco operators around the world deploying LTE networks!

It works too, while many ‘average’ users may have access to a VPN on their phone, not many would/could build their own VPN gateway on a laptop/router and have their phone use it! These minority are not on the radar of the operators to attempt to stop (and as you say is already mitigated to some degree by any cellular info the phone may be able to provide if not in airplane mode for any duration before attempting Wi-fi calling registration - as many people would forget to disable this for the entirety of their trip!!).


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[sbsnb]

Be careful that you'll get what you want with this method!

Have a VPN tunnel for your phone vs. having a job...

That is very good advice. In my specific case the worst I would get is a "don't do that," but it is important for people to be cognizant of the potential consequences of doing these sorts of things at work. In our case they just want to block all the people in the building (almost 5,000) from saturating the network with Netflix, Hulu, etc., but they don't know how to do it in a less restrictive way. Even if they knew exactly what I was doing it is unlikely that they'd care a whole bunch. It's one thing when you see a toddler with knife vs. an adult, if you know what I mean.

 

[rash.m2k]

Then have the router/laptop act as a VPN Client on behalf of the phone and problem solved

Just wanted to poke fun at that reason. I know my carrier zero rates WiFi calling but make sure airplane mode is on so it never hits cellular fallback .

This is the exact reason I joined this forum to try and fix this. I had used this exact situation with vodafone uk, throw the phone in airplane mode and enable wifi and bingo wifi calling abroad.

Now with ID mobile (aka 3 mobile) this doesn't work, so what I've done is setup a wifi hotspot on another phone with an app called VPN Hotspot (https://github.com/Mygod/VPNHotspot) so all traffic is routed via the VPN, this seems to work fine and route all traffic through the VPN - but still no wifi calling.

I know this thread is like almost 4 years old, but everywhere else on the mobile operators forums they don't have this level of information.

Anyone know how I can check what I'm doing wrong? What VPN service were you using? Any help to debug this would be great

 

[rash.m2k]

OK never mind I fixed it, by change the VPN protocol to Keepsolid Wise TLS.