buildah/docs/cni-examples/100-buildah-bridge.conf

{
    "cniVersion": "0.3.1",
    "name": "buildah-bridge",
    "type": "bridge",
    "bridge": "cni0",
    "isGateway": true,
    "ipMasq": true,
    "ipam": {
        "type": "host-local",
        "subnet": "10.88.0.0/16",
        "routes": [
            {
                "dst": "0.0.0.0/0"
            }
        ]
    }
}