Fedora 38 - how to to set up IP forwarding with iptables rules for Docker containers
I've been trying to set up IP forwarding in my Fedora 38 system to allow Docker containers to communicate with each other and the host network, but I'm working with some issues with my iptables configuration. I want to enable communication between a container on a custom bridge network and my host machine, but it seems like the traffic isn't being forwarded correctly. I've enabled IP forwarding by running: ```bash echo 1 > /proc/sys/net/ipv4/ip_forward ``` I also checked that this setting is persistent by adding `net.ipv4.ip_forward = 1` to `/etc/sysctl.conf` and then running `sysctl -p` to apply the changes. Here are the iptables rules I've set up: ```bash iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE iptables -A FORWARD -i docker0 -o eth0 -j ACCEPT iptables -A FORWARD -o docker0 -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT ``` After applying these rules, I verified them with `iptables -L -v -n` and they appear to be in place. However, when I run a test ping from a Docker container to an external IP (like 8.8.8.8), I get the following behavior: ``` ping: 8.8.8.8: Network is unreachable ``` I also checked the Docker network configuration using `docker network inspect bridge`, and everything seems fine there. My Docker version is 20.10.8, and I've ensured that the Docker service is running without issues. To troubleshoot further, I tried running a container in host networking mode with: ```bash docker run --network host --rm -it appropriate/curl curl 8.8.8.8 ``` This works perfectly, which indicates that it's not a general networking scenario. I'm unsure if there's something I'm missing with how Docker manages iptables or any additional configurations I need to consider. Any guidance or advice would be greatly appreciated!