Linux ppp0 and default route and how to reach public internet

my project needs mobile internet. I am trying to achieve this by using a LTE stick modem with a M2M sim (public IP, no NAT) This works well on ubuntu (5.3.0-29-generic), but I cannot get it working on Raspbian Buster (4.19.97+) Feb 11 22:31:48 raspberrypi systemd: Reloading. Feb 11 22:31:51 raspberrypi systemd: getty@tty1.service: Current command vanished from the unit file, execution of the command list won't be resumed. Feb 11 22:31:51 raspberrypi systemd: serial-getty@ttyAMA0.service: Current command vanished from the unit file, execution of the command list won't be resumed. Feb 11 22:32:00 raspberrypi systemd: Reloading. Feb 11 22:32:41 raspberrypi pppd: pppd 2.4.7 started by root, uid 0 Feb 11 22:32:41 raspberrypi pppd: Using interface ppp0 Feb 11 22:32:41 raspberrypi pppd: Connect: ppp0 /dev/ttyUSB1 Feb 11 22:32:41 raspberrypi NetworkManager: [1581460361.7138] manager: (ppp0): new Ppp device (/org/freedesktop/NetworkManager/Devices/5) Feb 11 22:32:42 raspberrypi pppd: CHAP authentication succeeded: Welcome!! Feb 11 22:32:42 raspberrypi pppd: CHAP authentication succeeded Feb 11 22:32:42 raspberrypi pppd: Could not determine remote IP address: defaulting to 10.64.64.64 Feb 11 22:32:42 raspberrypi pppd: not replacing default route to eth0 [192.168.0.1] Feb 11 22:32:42 raspberrypi pppd: local IP address 10.217.44.214 Feb 11 22:32:42 raspberrypi pppd: remote IP address 10.64.64.64 Feb 11 22:32:42 raspberrypi pppd: primary DNS address 109.249.185.224 Feb 11 22:32:42 raspberrypi pppd: secondary DNS address 109.249.186.32 Feb 11 22:32:42 raspberrypi NetworkManager: [1581460362.2378] device (ppp0): state change: unmanaged -> unavailable (reason 'connection-assumed', sys-iface-state: 'external') Feb 11 22:32:42 raspberrypi NetworkManager: [1581460362.3090] device (ppp0): state change: unavailable -> disconnected (reason 'none', sys-iface-state: 'external') Feb 11 22:35:30 raspberrypi pppd: Terminating on signal 15 Feb 11 22:35:30 raspberrypi pppd: Connect time 2.8 minutes. Feb 11 22:35:30 raspberrypi pppd: Sent 0 bytes, received 0 bytes. Feb 11 22:35:30 raspberrypi NetworkManager: [1581460530.4393] device (ppp0): state change: disconnected -> unmanaged (reason 'connection-assumed', sys-iface-state: 'external') Feb 11 22:35:30 raspberrypi pppd: Connection terminated. For this, I tried using wvdial with these settings [Dialer Defaults] Auto DNS = yes Init1 = ATZ+CFUN=1 Init2 = ATH Init3 = ATE1 Init3 = AT+CGDCONT=1,"IP","EEM2M" Stupid mode = 1 Baud = 9600 Dial Command = ATD Modem = /dev/ttyUSB1 ISDN = 0 Phone = *99# Password = bt Username = bt NetworkManager.conf has this content [main] plugins=ifupdown,keyfile [ifupdown] managed=false ppp/resolv.conf has this content nameserver 109.249.185.224 nameserver 109.249.186.32 I think this was set by the setup (see log above) Last but not least, this shows when I do ifconfig -a after wvdial is running. Note that the 6 packets in ppp0 are internal pings to 10.217.44.214 eth0: flags=4163 mtu 1500 inet 192.168.0.12 netmask 255.255.255.0 broadcast 192.168.0.255 inet6 fe80::b435:fc5d:b267:a226 prefixlen 64 scopeid 0x20 ether 00:e0:92:00:15:f3 txqueuelen 1000 (Ethernet) RX packets 299 bytes 30739 (30.0 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 269 bytes 36598 (35.7 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 lo: flags=73 mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1000 (Local Loopback) RX packets 4 bytes 156 (156.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 4 bytes 156 (156.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 ppp0: flags=4305 mtu 1500 inet 10.217.44.214 netmask 255.255.255.255 destination 10.64.64.64 ppp txqueuelen 3 (Point-to-Point Protocol) RX packets 6 bytes 66 (66.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 7 bytes 129 (129.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 wwan0: flags=4098 mtu 1500 ether 00:1e:10:1f:00:00 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 Edit 1: When running wvdial as root, I get this: --> WvDial: Internet dialer version 1.61 --> Initializing modem. --> Sending: ATZ+CFUN=1 OK --> Sending: ATH OK --> Sending: AT+CGDCONT=1,"IP","EEM2M" OK --> Modem initialized. --> Sending: ATD*99# --> Waiting for carrier. CONNECT 150000000 --> Carrier detected. Starting PPP immediately. --> Starting pppd at Tue Feb 11 23:01:49 2020 --> Pid of pppd: 1281 --> Using interface ppp0 --> pppd: X?CX?C --> pppd: X?CX?C --> pppd: X?CX?C --> pppd: X?CX?C --> pppd: X?CX?C --> pppd: X?CX?C --> local IP address 10.217.44.214 --> pppd: X?CX?C --> remote IP address 10.64.64.64 --> pppd: X?CX?C --> primary DNS address 109.249.185.224 --> pppd: X?CX?C --> secondary DNS address 109.249.186.32 --> pppd: X?CX?C I also noticed that when wvdial is running, the NetworkManager will load the correct DNS in /etc/resolv.conf, changing # Generated by NetworkManager nameserver 194.168.4.100 nameserver 194.168.8.100 to nameserver 109.249.185.224 nameserver 109.249.186.32 # Generated by NetworkManager