Bridge networking configuration to access host from inside pods

[GuillermoGarces]

I need to access services running on host from inside pods but host IP is not reacheable.
I was able to make it work using "--network host" option when creating cluster

k3d cluster create "k3d-cluster" \
    --network host \
    --k3s-arg '--flannel-backend=none@server:*' \
    --k3s-arg "--disable=traefik@server:*" \

Note: I am using calico and Ingress nginx, so I disabled flannel and traefik

... but I want to make it work using the custom bridge network that is created by k3d.

 k3d cluster create "k3d-cluster" \
    --k3s-arg '--flannel-backend=none@server:*' \
    --k3s-arg "--disable=traefik@server:*" \
    --api-port 6550 \
    -p "80:80@loadbalancer" \
    -p "443:443@loadbalancer" \

Is there a way to do it?

When a run a busybox from docker I can ping the host IP from inside the container.

docker run -it --rm busybox
> ping xxx.xxx.xxx.xxx

When I run a busybox as a pod in k3d and ping host IP, it is not reacheable.

kubectl run -i --tty busybox --image=busybox -- sh
> ping xxx.xxx.xxx.xxx

[iwilltry42]

Hi @GuillermoGarces , thanks for starting this discussion!
Have you tried referring to your host via host.k3d.internal within the cluster?

What's the system you're running on? Linux? Docker for Desktop on Win or Mac?

[GuillermoGarces]

Hello @iwilltry42 thank you for your help.
I am using Ubuntu 21.04

I have found the issue.
As I do with k3s ... I have installed calico as a replacement of flannel.
But I have found that it seems that k3d does not require a network fabric when running on docker

When I removed calico from my installation ... everything worked as expected.
Host can be ping from pods. It also works if you use host.k3d.internal

I would like in the future to install calico and make it work.
If somebody has any idea what should be configured for it to work, I would be happy to hear it.

[iwilltry42]

Nice that it works for you 👍
Doesn't this guide work for you? https://k3d.io/v5.2.2/usage/advanced/calico/#use-calico-instead-of-flannel

[GuillermoGarces]

I installed calico with the official helm chart
helm install calico projectcalico/tigera-operator

That might be the issue ... I did not allow IP forwarding as explained in the link
"container_settings": {
"allow_ip_forwarding": true
}

Thanks.

[iwilltry42]

Aaah, there's also an issue with the setup of the tigera operator as can be read over here: #898

[GuillermoGarces]

Official answer is that it should work out of the box if the network fabric is configured correctly as explained in https://k3d.io/v5.2.2/usage/advanced/calico/#use-calico-instead-of-flannel.

Or just installing k3d without disabling flannel