Cannot access host from docker on eth0

[maciekish]

Hi,

I have one network adapter in my unRAID box, eth0. I have set up Caddy with its own ip on eth0 in Docker as a reverse proxy for multiple services and subdomains. I want a reverse proxy for the unRAID interface as well, but i get 502 Bad Gateway. If i do

docker exec -it Caddy bash

and then try to ping the host IP it times out. Seems like the traffic is blocked or not properly routed. How do i fix this?

 

Network is 10.0.0.0/22

Host is 10.0.1.0 on eth0

Caddy is 10.0.1.12 on eth0 in Docker

I'm able to ping other devies in the network for example the router at 10.0.0.1.

[ken-ji]

That's a limitation inherent with technology / security used by the custom docker networks.

The container with a dedicated IP on eth0 (Caddy in your case) is explicitly not allowed to talk to host (unRAID) due to Linux kernel security measures.

 

The only way around it, is to: (in order of difficulty)

* have a second interface (the custom network is on this interface)

* have VLAN support and locate the  container on a different VLAN than the host

 

You can refer to these topics for some more details.