Linux @lemmy.ml DM294 @lemm.ee 8 mo. ago

Hotspot Wi-Fi connected to my laptop works without connected to mobile data. What could be the reason?

Title is self explanatory. For background, I am currently running Asahi Linux on my M1 MBP. Whenever I connected the hotspot without data being turned on, it somehow still worked like any regular wifi. I even ran several updates in the system and downloaded multiple apps in this wifi, which I find it amusing. But out of curiosity, I wanted to know from you guys that what could the reason be for this.

EDIT: So after following the advice of jet@hackertalks.com, I relized that the hotspot is using the network of my University's Wi-Fi, which explains why the hotspot worked even with the data turned off.

27 comments

Is the wifi enabled and connected on the phone? I had a situation once where the hotspot network was relaying data to the connected wifi network on the phone instead of mobile data like you'd expect.
- That would be my guess as well.
- Yeah my phone does this
- Yeah, the Wi-Fi on my phone is enabled.
Do a traceroute and see which network it transits through
- Ok, so after running traceroute, it seems that the hotspot is using the network of my university Wi-Fi, which my phone is connected with. EDIT: Thanks a lot! Forgot to thank you for the advice 😅
  
  It's interesting on it's own, since I do remember my android phone disconnecting from wifi when enabling the hotspot. If I understand it right, this type of wifi bridge requires two radios to work efficiently, but it may have changed in latest Wi-Fi standards. Curious nontheless.
  
  Which phone is that? I thought that most phones could not create a hotspot and at the same time connect to a WiFi network.
  
  Is the phone essentially acting as a fancy Layer 3 extender?
So, you have a phone that does the tethering or something? Maybe, It's some bug on its (or their, depending on how close you two are) side? I'd try another device with the same hotspot.

Alternatively, the laptop may be connected to several networks at the same time and be using whatever works. Can probably be checked by verifying ips of the phone and the laptop.
- So this same thing ocurred when my laptop was connected to the hotspot of my previous phone under a different name.
A hotspot is a connection where your phone creates a wifi network using its wifi antenna. The signal strength depends on how far away the phone is, thats it.

The hotspot stays on also if the phone has no cell data connection. Normally a phone should only be able to connect to either a wifi or be a hotspot, phone model is important.
Unrelated but what theme/color scheme are you using?
- I am using the default Breeze Dark Theme, with colours from Sweet-Ambar-Blue.
  
  Thanks!
Is tethering overriding your data setting? If it was truly offline updates etc wouldn’t work
- All the tethering settings are off. I'm just using the default hotspot settings.
  
  https://en.wikipedia.org/wiki/RNDIS (connectivity over usb)
  
  my samsung phone gives me several options (charging,mtp,rndis,etc..)
  its surprising that your tethering is off. it might seem that its considered a seperate technology.
  
  edit: "RNDIS linux module is being deprecated and will be removed from the Linux Kernel in favor Network Control Model (NCM), but it is used by majority of devices nowadays (2023) and up to now the only way to configure working USB tethering for old Android devices.[1] For more recent devices (Android 14 era) try to use "Network Control Model (NCM) support" module first."
You could also try to ping 8.8.8.8 (or whatever public IP you can remember). If it works it is not getting a correct DNS which results in "no connection"

In this case modify your connection on the laptop to use 8.8.8.8 (google) or 208.67.222.222 (opendns) and check if it works

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