Docker network internet access

Selfhosted@lemmy.world – 18 points – 4 months ago

Hey all! I'm having an issue that's probably simple but I can't seem to work it out.

For some history (just in case it matters): I have a simple server running docker and all services being defined in docker-compose files. Probably doesn't matter, but I've switched between a few management UIs (Portainer, Dokemon, currently Dockge). Initially, I set everything up in Portainer (including the main network) and migrated everything over to Dockge. I was using Traefik labels but was getting a bit annoying since I tend to tinker on a tablet. I wanted something a bit more UI-focused so I switched to NPM.

Now I'm going through all of my compose files and cleaning up a bunch of things like Traefik labels, homepage labels, etc... but I'm also trying to clean up my Docker network situation.

My containers are all on the same network, and I want to slice things up a little better, e.g. I have the Cloudflared container and want to be selective about what containers it has access to network-wise.

So, the meat of my issue is that my original network (call it old_main) seems to be the only one that can access the internet outbound. I added a new network called cloudflared and put just my Cloudflared container and another service on it and I get the 1033 ARGO Tunnel error when accessing the service and Cloudflare says the tunnel is down. Same thing for other containers I try to move from old_main, SearXNG can't connect, Audiobookshelf can't search for author info, etc... I can connect to these services but they can't reach anything on the web.

I have my docker daemon.json set to use my Pi-hole for DNS and I only see my services like audiobookshelf.old_main coming through. I also see the IP address of the old_main gateway coming into Pi-hole as docker-host. My goal is to add all of my services to new, more-specific networks then remove old_main but I don't want to drop the only network that seems to be able to communicate with the web until I have another that can.

I'm not sure what else to look for, any suggestions? Let me know if you need more info.

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It sounds like your issue might be related to how your Docker networks are configured for DNS and internet access. Try these:

Check Network Configuration: Ensure your new networks are correctly configured to allow internet access. Docker networks should be able to route traffic to the internet by default unless specified otherwise.
DNS Configuration: Since you're using Pi-hole for DNS, make sure the new networks are properly configured to use Pi-hole as their DNS server.
Inspect Network Settings: Compare the settings of old_main with the new networks. Use the following command to inspect the network configuration:
```
docker network inspect old_main
docker network inspect cloudflared
```
Pay attention to the gateway, subnet, and any custom DNS settings.
Check Docker Daemon Configuration: Verify that your daemon.json file is correctly set up to use Pi-hole for DNS. It should look something like this:
```
{
  "dns": [""]
}
```
Verify Container Configuration: Ensure that your containers are correctly configured to use the new network. This can be specified in your docker-compose files like this:
```
version: '3.7'
services:
  cloudflared:
    image: cloudflare/cloudflared
    networks:
      - cloudflared

networks:
  cloudflared:
    external: true
```
Check Firewall Rules: Ensure there are no firewall rules on your host or network equipment that might be blocking traffic from the new networks.
Test Connectivity: Run a simple connectivity test from within a container on the new network to check internet access:
```
docker run --rm -it --network cloudflared alpine ping -c 4 google.com
```
If this fails, the issue is likely with network configuration rather than the containers themselves.
Docker Network Restart: Sometimes, Docker networks need to be restarted to apply changes correctly. Try removing and recreating the problematic networks:
```
docker network rm cloudflared
docker network create cloudflared
```

If none of the above steps resolve the issue, there might be a deeper configuration problem. At this point, it might be helpful to see the exact configuration of your docker-compose files and the output of the network inspection commands.

This sounds like a chat gpt answer.

Definitely.