Set network interface priority

cf: https://forums.raspberrypi.com/viewtopic.php?t=278033  

For linux: 

First run the command:

route -n 

It will show the metrics of the interface. 

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.2.1     0.0.0.0         UG    202    0        0 eth1
0.0.0.0         192.168.1.12    0.0.0.0         UG    303    0        0 wlan0
 

The lower the route priority first. So eth0 is higher than wlan0.

Edit /etc/dpchcd.conf: 

interface wlan0 

metric 100 

And run route -n, it will then show:


 

Kernel IP routing table 

Destination Gateway Genmask Flags Metric Ref Use Iface


0.0.0.0 192.168.1.12 0.0.0.0 UG 100 0 0 wlan0 

0.0.0.0 192.168.2.1 0.0.0.0 UG 204 0 0 eth1  

 

Thus, wlan0 will is higher than eth1. 

Becuase wlan0 is the external interface, while eth1 is for internal interface, the wlan0 priority need to be higher than eth1. Otherwise, the outside internet can not be reached. 

 

For windows:

The following image shows the NIC is set to metric 5.