Cannot delete default gateway, when docker container is running

Question

I want to remove a default route from my Raspberry Pi running Raspbian.

This is what I get from route -n:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.178.1   0.0.0.0         UG    203    0        0 eth1
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 veth07ba603
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 docker0
192.168.178.0   0.0.0.0         255.255.255.0   U     203    0        0 eth1

I tried the following commands to remove the gateway:

ip route del default via 192.168.178.1 dev eth1
route del default gw  192.168.178.1
route del default gw  192.168.178.1 dev eth1
route del -net 0.0.0.0 gw 192.168.178.1 netmask 0.0.0.0 dev eth1
ip route del 0.0.0.0/0

None of them works.

If I run route -n again the route is still there and I can still reach the internet.

Syslog looks fine too:

Dec  3 02:42:21 pi dhcpcd[474]: eth1: deleted default route via 192.168.178.1

Upadte:

I figured out that the issue only appears if I run a docker container, e.g:

docker run --name 'foo' -itd alpine /bin/sh

If the container is turned off, I can delete the gateway. But for some reason docker re-creates the default gateway if I start the container with docker start foo. If the container is running, I cannot delete the gateway at all (see above).

Does anyone know what's happening here? How can I run the container without the default gateway? The Pi should not have an internet connection.

Answer 1

The solution was to assign a static ip to the Pi by adding the following lines to /etc/dhcpcd.conf:

interface eth1
static ip_address=192.168.178.10

I can now add and del the default gateway like expected, no matter if the docker container is running or not.