How can I set the destination to "anywhere" in the iptables?

As far as i understood with the following rule:

ACCEPT tcp -- anywhere 172.17.0.4 tcp dpt:25565

ubuntu allows connection via port 25565 but only to 172.17.0.4, but i want it to be reachable from anywhere. Ive tried something like

sudo iptables -A INPUT -p tcp --dport 25565 -j ACCEPT -d anywhere

but that doesn't work. Am I missing something? Maybe im totally wrong i don't know much about networking. My server i want to reach runs in a docker container if that makes any differences.

2 Answers

You can omit the "-d ...", but INPUT is just to your local device.

When your destination is in another network (even if it is a virtual network) you need forwarding:

echo 1 > /proc/sys/net/ipv4/ip_forward

And the FORWARD chain is the right place to put your rules (but "ACCEPT" should already be the default)

Hint: iptables -S outputs the rules in the command-format

You can execute command below to do that

sudo iptables -I INPUT -p tcp --dport 25565 -j ACCEPT