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I'm trying to achieve the following with my RPi3:

  • Static eth0 IP. This connects to my car's infotainment system.
  • DHCP wlan0 IP. This is for the RPi3 to connect to my home Wifi while the car is in the garage
  • Both eth0 and wlan0 must be up at the same time
  • I have no need to route traffic from the car's infotainment system through the RPi to Wifi or vice-versa (actually I want to prevent this)

My current situation is, with the /etc/network/interfaces file below, the wlan0 is working fine, but eth0 has no IP address and is unusable.
When I add "inet" to the iface eth0 configuration line, eth0 gets the static IP address, but wlan0 ceases to work. The wlan0 IP assigned to RPi by Wifi equipment is 192.168.1.20; netmask is 255.255.255.0.

auto lo
iface lo inet loopback

auto eth0
iface eth0 static
address 192.168.42.1
netmask 255.255.255.0
# Car's infotainment IP 192.168.42.3

allow-hotplug wlan0
auto wlan0
iface wlan0 inet dhcp
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
Jason G
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2 Answers2

1

What you have has a number of errors, and would not have worked.

Indeed the proper configuration would NOT have enabled both interfaces simultaneously. dhcpcd will configure both (if correctly setup).

See How do I set up networking/WiFi/Static IP

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Milliways
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1

What worked for me (can communicate with Pi from eth side and wlan side):

/etc/network/interfaces

auto wlan0
auto lo
iface lo inet loopback

allow-hotplug eth0
inet eth0 inet manual

allow-hotplug wlan0
iface wlan0 inet manual

/etc/wpa_supplicant/wpa_supplicant.conf:

network={
ssid="MYSSID"
key_mgmt=WPA-PSK
proto=RSN
psk="MYPSK"
}

/etc/dhcpcd.conf (using 192.168.42.2 as Pi IP and 192.168.42.1 as Car IP)

interface eth0
static ip_address=192.168.42.2/24
static routers=192.168.42.1
static domain_name_servers=192.168.42.1 8.8.8.8

interface wlan0
static ip_address=undefined/24
static routers=undefined
static domain_name_servers=undefined 8.8.8.8
Jason G
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