[Beaglebone Enhanced][VAYU2-4GEC25-E][Quectel] - Not work mobile connection if ethernet wire is plug

[Nicola Russo]

I'm using the cape model: VAYU2-4GEC25-E (https://www.yantrr.com/product/vayu2-4g-ltecat4asia-eu-w-gps/) together with a Beaglebone Enhanced that running on Debian 9.5 2018-10-07 4GB eMMC IoT .

I started ppp connection as described below with wvdial:
----------------------------------------------------------
debian@beaglebone:~$ sudo wvdial &

[1] 1288
debian@beaglebone:~$ --> WvDial: Internet dialer version 1.61
--> Initializing modem.
--> Sending: ATZ
ATZ
OK
--> Sending: ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
OK
--> Sending: at+cgdcont=1,"ip","[web.omnitel.it](http://web.omnitel.it/)"
at+cgdcont=1,"ip","[web.omnitel.it](http://web.omnitel.it/)"
OK
--> Modem initialized.
--> Sending: ATDT*99#
--> Waiting for carrier.
ATDT*99#
CONNECT 150000000
--> Carrier detected. Starting PPP immediately.
--> Starting pppd at Mon Jan 20 09:30:05 2020
--> Pid of pppd: 1290
--> Using interface ppp0
--> pppd: ▒^▒(9t[01][18]9t[01]
--> pppd: ▒^▒(9t[01][18]9t[01]
--> pppd: ▒^▒(9t[01][18]9t[01]
--> pppd: ▒^▒(9t[01][18]9t[01]
--> pppd: ▒^▒(9t[01][18]9t[01]
--> pppd: ▒^▒(9t[01][18]9t[01]
--> local IP address 5.91.117.101
--> pppd: ▒^▒(9t[01][18]9t[01]
--> remote IP address 10.64.64.64
--> pppd: ▒^▒(9t[01][18]9t[01]
--> primary DNS address 10.133.18.210
--> pppd: ▒^▒(9t[01][18]9t[01]
--> secondary DNS address 10.132.100.181
--> pppd: ▒^▒(9t[01][18]9t[01]
^C
debian@beaglebone:~$ ^C
debian@beaglebone:~$ ^C
debian@beaglebone:~$ ping [google.com](http://google.com/)
PING [google.com](http://google.com/) (216.58.208.142) 56(84) bytes of data.
64 bytes from [lhr25s08-in-f14.1e100.net](http://lhr25s08-in-f14.1e100.net/) (216.58.208.142): icmp_seq=1 ttl=50 time=47.7 ms
64 bytes from [lhr25s08-in-f14.1e100.net](http://lhr25s08-in-f14.1e100.net/) (216.58.208.142): icmp_seq=2 ttl=50 time=56.0 ms
64 bytes from [lhr25s08-in-f14.1e100.net](http://lhr25s08-in-f14.1e100.net/) (216.58.208.142): icmp_seq=3 ttl=50 time=48.9 ms

------------------------------------------

After I connected Ethernet wire of my subnet at beaglebone, so the mobile connection doesn't work anymore. Only if I disconnect Ethernet wire, the mobile connection works.

In the Debian System Is It possible to set a connection priority between 4G connection and internet connection by LAN wire?

I need to use 4g connection and ethernet port for TCPIP communications simultaneously.
In which configuration file can I set this priority?

[Tarmo Kuuse]

Hi Nicola,

The word to google for is network manager. Without a network ethernet and dialup are implemented by a set of bash scripts which don't consider each other and step on each other's toes. Typically the most annoying thing that happens is the connection which is established last will blindly overwrite DNS configuration for the previous. It might also overwrite the default route (or worse - NOT overwrite the default route in which case its provider-private DNS servers are likely unreachable from the other connection which effectively kills the Internet connection). There are many ways for this to fail. 

You need a network manager which is aware of both the Ethernet and dialup connections and can juggle the DNS servers, default routes and other resources according to configuration that you specify. AFAIK that they operate according to your requirements in tandem with their "friendly" dialup manager, so ppp and wvdial cannot be used.

Gnome project has NetworkManager with dialup companion ModemManager. This is intended for desktop usage and might be a wee bit demanding on resources or required libraries. I know very little about those two, so I might be wrong

The other is connman with dialup companion ofono. This is intended for lightweight embedded systems. Connman is likely installed on your system already, you just need to set up ofono to do the dialup. The downside is that both (especially ofono) are rather poorly documented and getting the whole thing up and running in tandem is a bit frustrating for a new user.

--

Kind regards,

Tarmo