Tips on how to Entry Ports on the Host from a Docker Container

Tips on how to Entry Ports on the Host from a Docker Container


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In the event you’re networking to the skin world, Docker behaves as if the request was coming from the host machine. However if you wish to entry processes which might be operating on the host, your firewall might have some further configuration.

The Answer: Add a Firewall Rule for 172.18.0.0/16

In the event you’ve simply tried to entry a course of operating on the host machine like an HTTP service, you may need gotten blocked. It is because despite the fact that Docker containers run on the host, they use some particular networking beneath the hood to maintain them logically separated, and due to that they’ve completely different IP addresses.

You may see this when operating ifconfig, you’ll see your normal community interface, but additionally the docker0 interface. By default, Docker makes use of the 172.18.0.0/16 block to allocate container IP addresses.

The docker0 interface

The repair may be very easy—open this port vary in your firewall. Requests from the IP vary Docker makes use of are possible getting blocked. It’s a non-public IP deal with vary, so there’s minimal danger in having it open. For UFW, that will be:

sudo ufw permit from 172.18.0.0/24

Optionally specifying a port to open:

sudo ufw permit from 172.18.0.0/24 to any port 9200

For iptables, that will be:

iptables --append INPUT --protocol tcp --src 172.18.0.0/24 --jump DROP

For managed internet hosting providers like AWS, it’s possible you’ll not want to vary something—safety teams are community firewalls that sit in entrance of situations, and shouldn’t have an effect on inside site visitors.



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