Multi-homed host breaks networking

I built an host to run ansible from. I made it a multi-homed host, following these instructions (https://access.redhat.com/solutions/288823). The point is to lock it down and limit access, since ansible has the keys to the kingdom.
I installed the AWX project (open source version of Tower, https://github.com/ansible/awx), which creates several containers.

My problem is that the containers can’t access anything off the host.
I’ve tried a couple of settings in my daemon.json file, but no joy.

{
"ip": "172.23.70.4",
"default-gateway": "172.23.70.1",
"bip": "172.31.0.1/16"
}

I can’t find anything referencing multihomed hosts with docker at all. Anyone have any ideas here?