Connection problems on mobile network

buggy

I installed openvpn server on a debian 11 server virtual machine (VirtualBox) on an ubuntu 22.04 LTS server host. using this script:
https://raw.githubusercontent.com/Nyr/openvpn-install/master/openvpn-install.sh .

I installed the openvpnclient on an android phone and imported the ovpn file generated by the install script.

forwarded port 1194 on my router to the vm.

The phone now connects to the server fine. Both from local LAN and WAN. Browsing my smb shares and connecting to internet works fine from LAN (wifi enabled on the phone). However, when I disable wifi and connect through my mobile network it will still connect fine, but accessing smb shares and internet websites will fail most of the times. Pinging google.com gave no errors and no lost packages.

I am new to vpn and clueless. Any help to point me in the right direction will be appreciated.

Pippin

Could it be that samba rejects traffic coming from a different subnet then itself resides on?
If so, it seems you need to allow that/those subnet(s):
https://www.oreilly.com/openbook/samba/book/ch04_06.html

buggy

Pippin wrote Could it be that samba rejects traffic coming from a different subnet then itself resides on?
If so, it seems you need to allow that/those subnet(s):
https://www.oreilly.com/openbook/samba/book/ch04_06.html

Please correct me if i am wrong, but I assumed the ip reported to samba would be the ip of tun0. So the subnet would be the same on LAN and WAN.

buggy

I did some investigation on the mobile network. "ip a" command returns 192.0.0.4 and an ip check online returns 77.63.xx.xxx . So it seems the mobile network is behind a nat router. Now it makes sense I have Issues.

I will try a different wifi network and see if it will work there

Still looking for a solution. The whole point of my vpn server is to connect to my home network on the road using the phones hotspot.

I guess have to change The subject title 🙂

buggy

I did a test on a friends wifi network and everything worked fine on both the android and a windows client. So this is not a samba configuration issue. Also the basic configuration of openvpn on both the server and the client seems okay.

I am still in the dark what to do about the bad connection on the mobile network.

I am using the udp protocol. I will change that to tcp. Maybe it will help if the server gets some feedback about lost packets.

buggy

Switched from udp to tcp. Connection is fine now, so I think guessed right. 🙂

Problem solved for now.

etherdolphin

buggy wrote I did some investigation on the mobile network. "ip a" command returns 192.0.0.4 and an ip check online returns 77.63.xx.xxx . So it seems the mobile network is behind a nat router. Now it makes sense I have Issues.

I will try a different wifi network and see if it will work there

Still looking for a solution. The whole point of my vpn server is to connect to my home network on the road using the phones hotspot.

I guess have to change The subject title 🙂

I'm fighting the same issue and as I currently own a spare mobile carrier connectivity, I've discovered that using the mobile network of one of the mobile carrier, my VPN works fine both using UDP and TCP whereas the other ISP mobile network works only using TCP protocol.
This happens on Android version 14 and "OpenVPN Connect" app version 3.4.0.
Client side, the "OpenVPN Connect" app logs does not show any relevant clue, just a connection timeout message. I've also tested that there where no problems trying to send and receive UDP packets on Android using a terminal app.

Server side, during my tests, I've found that:

tcpdump -ni <my_network_interface> udp and port <my_openvpn_listening_port>

reports some incoming packets but the OpenVPN server running in a terminal session does report nothing. I've also tried with a different port and, yes, obviously I've tried completely disabling the running firewall and my router ports are correctly forwarded.

Temporarily solved using TCP, altough connection seems generally very slow.

A further test demonstrates that using the mobile carrier which as stated above worked only in TCP mode, also works using UDP protocol with a Linux laptop configured as OpenVPN client, connected throught the Android phone used as mobile wifi hotspot.
This seems really no-sense, I can only think of the involved mobile carrier blocking some packets for some unknown reason.