@xes
Never used mssfix 1400 on my openvpn config on my N900 and vpn always worked. BTW my gprs0 MTU is 1400 and not 1464... !?

@fw190
You say that ping 8.8.8.8 gives an output but you don't say if it's a ping reply or an error. If it's a ping reply then most likely it is a DNS issue. If it's an error then we need to dig more deeply.

If the output of ping 8.8.8.8 is an error then try to do what Macros suggested. Change the verb variable from 1 to 5 in your config file and start openvpn from the command line (you may need to become root before executing this command) :
openvpn --config /path/to/your/file.conf

Provide the output here (check for any sensitive info before posting the output on the forum).

@Malakai
i'm sorry, sometimes i forget the tweaks applied during the years.

gprs0 interface has default mtu at 1400 but can transport packets up to 1464 (= real mtu is 1464)

So, to gain a bit of speed (4-5%) you can tweak that value with:

ifconfig gprs0 mtu 1464

and you can check this with:

ping -M do -s 1436 8.8.8.8

(since 1436 + 20 bytes for ip headers + 8 bytes of icmp request = 1464)

Trying 1437 will fail returning no packets transmitted.

Now, about opevpn, it seems that mtu discovery is a little bit messy resulting that the parameter "mtu-disc yes" produces long connection times and some strange behaviors (openvpn developers still suggest to avoid mtu-disc and fix things adjusting by hand the mtu on both sides or using the mssfix option)

So here we are, mssfix should consider the real mtu less the openvpn overhead due the tunnel encapsulation (it changes with udp/tcp)
Openvpn howto suggest to start trying with some values 1200,1300,1400 to discover if it fixes the transmission problems.
In fact, with N900 stock mtu at 1400, mssfix must be near 1300 (i'm sorry at the moment i can't point you to a proper page describing detailed openvpn overhead calculation)

After this confusion and i hope explanation, maybe fw190 has still some other (basic) trouble with maybe a dns failure or a missing proxy setting required by that provider.

Ping 8.8.8.8 from termnal with vpn started from plugin:

-- 8.8.8.8 ping statistics ---
25 packets transmitted, 25 packets received, 0% packet loss
round-trip min/avg/max = 168.671/212.821/580.993 ms
Nokia-N900:~#

The same was the last time but I could not stop it from pinging and had to close the terminal.

starting the vpn from command line gives a bunch of errors - as I understand the are posted because of missing data in config file which is pulled from the folder by the aplet when starting vpn.

Nokia-N900:~# openvpn --config /etc/openvpn/Germany.ovpn
Options error: --ca fails with 'ca.crt': No such file or directory
Options error: --crl-verify fails with 'crl.pem': No such file or directory
Options error: --auth-user-pass fails with 'pass.txt': No such file or directory
Options error: Please correct these errors.
Use --help for more

You need to type the full path to where ca.crt, crl.pem and pass,txt are located (in your config file)

As nieldk says you should put the full path for each file, I have mines in :
/home/user/MyDocs/.documents/vpn/

Also you seem to get a reply from 8.8.8.8 but I think that it is using your gprs0 interface (as the vpn doesn't seem to be up).

Try first to fix the path to the ca.crt, crl.pem and pass.txt and try to connect again.

I have changed the config file:

Nokia-N900:~# openvpn --config /etc/openvpn/Finland.ovpn
Sat Aug 13 09:24:18 2016 OpenVPN 2.3.10 arm-unknown-linux-gnueabi [SSL (OpenSSL)] [LZO] [EPOLL] [MH] [IPv6] built on Feb 10 2016
Sat Aug 13 09:24:18 2016 library versions: OpenSSL 0.9.8zf 19 Mar 2015, LZO 2.03
Sat Aug 13 09:24:18 2016 WARNING: file '/etc/openvpn/pass.txt' is group or others accessible
Sat Aug 13 09:24:20 2016 UDPv4 link local: [undef]
Sat Aug 13 09:24:20 2016 UDPv4 link remote: [AF_INET]192.40.95.7:1194
Sat Aug 13 09:24:20 2016 WARNING: this configuration may cache passwords in memory -- use the auth-nocache option to prevent this
Sat Aug 13 09:24:22 2016 [9553934360ce5f7a5fee894d130eab0c] Peer Connection Initiated with [AF_INET]192.40.95.7:1194
Sat Aug 13 09:24:25 2016 TUN/TAP device tun0 opened
Sat Aug 13 09:24:25 2016 do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0
Sat Aug 13 09:24:25 2016 /sbin/ifconfig tun0 10.164.1.6 pointopoint 10.164.1.5 mtu 1500
Sat Aug 13 09:24:25 2016 Initialization Sequence Completed


but the browser could not load any page. The internet connection was already established before starting the vpn from terminal. Generally the plugin gives very simillar output. With wi-fi I always start wi-fi then vpn from plugin and it works ok.

And pingign 8.8.8.8 with gprs and vpn started from plugin gives:
64 bytes from 8.8.8.8: seq=1 ttl=46 time170.929 ms and so on until I stop it. When I stop it there are no lost packages

By default, web traffic is not routed through VPN tunnel.
You should have a look here on how to redirect all traffic through the VPN, including web.

https://openvpn.net/index.php/open-s....html#redirect

You also need to configure pushing DNS to the client, with a config option like this

dhcp-option DNS 10.11.12.1

Change the IP to your DNS server

I just don't understand why it works over Wi-Fi, and not over cellular?

And why it works with openvpn on Android both on Wi-Fi and cellular?

Same cellular, same VPN, openvpn and... It refuses to cooperate with me

Well, for one, the configuration is different.
The Android client may seek certain parameters, like DNS, by default

Why do I have to do all of this for cellular and not for wi-fi?

I think that it is to much for me and I will leave it as is.