How to use slack auth running in docker from within a private IP addressed enterprise network

We are deploying our application in docker within our enterprise. The host machine has an RFC1918 space in the 10/8 network and the docker containers are on 172.21/16 space.

I’m trying to use slack authentication to authenticate our node/react application which works locally in development mode, but I believe the second layer of private address space may be throwing a wrench into the communications. The redirect url for the node/react app is using the IP of the host machine, which is what you are hitting when you attempt to login to the server via the web interface. I’ve tried many combinations but basically you navigate to 10.1.1.4:3000 which is configured in the Slack API as our redirect URL and is also configured in the .env file for our node app. Once you click continue on the slack auth page the page doesn’t load but just hangs.

I’ve changed the redirect URL to localhost, the gateway IP of the docker network, and the IP address of the host machine the docker container is running on, which I think is the way to go, but nothing lets me hit my app.

Source: StackOverflow