mjhjmtu

Whenever I add my 4G modem to my raspberry, it gets on top of the default routes ou ip route list, however I want everything to go through wlan, and only use the 4G modem to receive SSH connections.

I've found this answer on how to disable the default routes: https://serverfault.com/a/836708

however, after reboot, the 4G modem comes back to the top.

How do I make wlan0 to always be the first rule on default?

UPDATE:

Here's the dmesg output when I connect the USB dongle:

[426102.910168] usb 1-1.5.1: new full-speed USB device number 6 using dwc_otg
[426103.046670] usb 1-1.5.1: not running at top speed; connect to a high speed hub
[426103.056674] usb 1-1.5.1: New USB device found, idVendor=12d1, idProduct=1f01
[426103.056693] usb 1-1.5.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[426103.056704] usb 1-1.5.1: Product: HUAWEI_MOBILE
[426103.056714] usb 1-1.5.1: Manufacturer: HUAWEI_MOBILE
[426103.056724] usb 1-1.5.1: SerialNumber: 0123456789ABCDEF
[426103.121355] usb-storage 1-1.5.1:1.0: USB Mass Storage device detected
[426103.122875] scsi host0: usb-storage 1-1.5.1:1.0
[426103.987177] usb 1-1.5.1: USB disconnect, device number 6
[426105.470211] usb 1-1.5.1: new full-speed USB device number 7 using dwc_otg
[426105.606666] usb 1-1.5.1: not running at top speed; connect to a high speed hub
[426105.615673] usb 1-1.5.1: New USB device found, idVendor=12d1, idProduct=14dc
[426105.615692] usb 1-1.5.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[426105.615703] usb 1-1.5.1: Product: HUAWEI_MOBILE
[426105.615713] usb 1-1.5.1: Manufacturer: HUAWEI_MOBILE
[426105.766297] usb-storage 1-1.5.1:1.2: USB Mass Storage device detected
[426105.766768] scsi host0: usb-storage 1-1.5.1:1.2
[426105.855053] cdc_ether 1-1.5.1:1.0 eth1: register 'cdc_ether' at usb-3f980000.usb-1.5.1, CDC Ethernet Device, 0c:5b:8f:27:9a:64
[426105.855593] usbcore: registered new interface driver cdc_ether
[426106.785653] scsi 0:0:0:0: Direct-Access HUAWEI TF CARD Storage 2.31 PQ: 0 ANSI: 2
[426106.803758] sd 0:0:0:0: Attached scsi generic sg0 type 0
[426106.820687] sd 0:0:0:0: [sda] Attached SCSI removable disk

Here's ip addr

eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
 link/ether 0c:5b:8f:27:9a:64 brd ff:ff:ff:ff:ff:ff
 inet6 fe80::584f:751f:bb3e:e26b/64 scope link 
 valid_lft forever preferred_lft forever

UPDATE 2

I attached it a few more times until it showed the eth1 route:

[10787.229141] usb 1-1.5: new full-speed USB device number 7 using dwc_otg
[10787.363515] usb 1-1.5: New USB device found, idVendor=05e3, idProduct=0606
[10787.363533] usb 1-1.5: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[10787.363544] usb 1-1.5: Product: USB Hub 2.0
[10787.363555] usb 1-1.5: Manufacturer: ALCOR
[10787.365166] hub 1-1.5:1.0: USB hub found
[10787.369831] hub 1-1.5:1.0: 4 ports detected
[10797.419094] usb 1-1.5.1: new full-speed USB device number 8 using dwc_otg
[10797.555636] usb 1-1.5.1: not running at top speed; connect to a high speed hub
[10797.565759] usb 1-1.5.1: New USB device found, idVendor=12d1, idProduct=1f01
[10797.565777] usb 1-1.5.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[10797.565789] usb 1-1.5.1: Product: HUAWEI_MOBILE
[10797.565799] usb 1-1.5.1: Manufacturer: HUAWEI_MOBILE
[10797.565808] usb 1-1.5.1: SerialNumber: 0123456789ABCDEF
[10797.630477] usb-storage 1-1.5.1:1.0: USB Mass Storage device detected
[10797.631101] scsi host0: usb-storage 1-1.5.1:1.0
[10798.472745] usb 1-1.5.1: USB disconnect, device number 8
[10799.469081] usb 1-1.5.1: new full-speed USB device number 9 using dwc_otg
[10799.630768] usb 1-1.5.1: not running at top speed; connect to a high speed hub
[10799.646891] usb 1-1.5.1: New USB device found, idVendor=12d1, idProduct=14dc
[10799.646909] usb 1-1.5.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[10799.646920] usb 1-1.5.1: Product: HUAWEI_MOBILE
[10799.646930] usb 1-1.5.1: Manufacturer: HUAWEI_MOBILE
[10799.814489] usb-storage 1-1.5.1:1.2: USB Mass Storage device detected
[10799.815008] scsi host0: usb-storage 1-1.5.1:1.2
[10799.897788] cdc_ether 1-1.5.1:1.0 eth1: register 'cdc_ether' at usb-3f980000.usb-1.5.1, CDC Ethernet Device, 0c:5b:8f:27:9a:64
[10799.898127] usbcore: registered new interface driver cdc_ether
[10800.889652] scsi 0:0:0:0: Direct-Access HUAWEI TF CARD Storage 2.31 PQ: 0 ANSI: 2
[10800.910585] sd 0:0:0:0: Attached scsi generic sg0 type 0
[10800.923297] sd 0:0:0:0: [sda] Attached SCSI removable disk

Here's route -n

Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 wlan0
0.0.0.0 192.168.8.1 0.0.0.0 UG 207 0 0 eth1
0.0.0.0 192.168.1.1 0.0.0.0 UG 303 0 0 wlan0
169.254.0.0 0.0.0.0 255.255.0.0 U 202 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 204 0 0 docker0
169.254.0.0 0.0.0.0 255.255.0.0 U 206 0 0 veth4557ad2
172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 wlan0
192.168.1.0 0.0.0.0 255.255.255.0 U 303 0 0 wlan0
192.168.8.0 0.0.0.0 255.255.255.0 U 207 0 0 eth1

See that I did ifmetric wlan0 in order to be able to use the wlan0 to ssh into my raspberry

For changing the routing priority for an interface you change metrics.

By default, all are 0, which is the highest priority. So, you can do:

allow-hotplug eth1
iface eth1 inet dhcp
 up ifmetric eth1 30

To use ifmetric in Debian, you have got to install it:

sudo apt-get install ifmetric

ifmetric

Set routing metrics for a network interface

ifmetric is a Linux tool for setting the metrics of all IPv4 routes
attached to a given network interface at once. This may be used to
change the priority of routing IPv4 traffic over the interface. Lower
metrics correlate with higher priorities.

The metric 0 means the highest priority route and is the default one.
The larger metric value means lower priority routes. The IP address of
the active interface with the lowest metric value becomes the
originating one. See ifmetric(8).

One way to Persist the ip route add/del in debian is to write them down into /etc/network/interfaces like below:

allow-hotplug eth1
iface eth1 inet dhcp
 post-up ip route del default
 post-up ip route add default via <gateway IP> dev wlan0

I think the matter on default gateway. Here is the tutorial.

I briefly explain the steps. First, you need to delete the default gateway and add the one you want to add. Then, you edit "/etc/network/interfaces" for permanent change. Finally, you restart the service.

https://www.wikihow.com/Add-or-Change-the-Default-Gateway-in-Linux