I’ve been hard time to figure out why my openstack doesn’t communicate with outside and it’s always saying ‘Down’ when I checked external network in router.

It turned out that is the issue with ‘promiscuous mode’. In default, it’s requires to have authentication for entering promiscuous mode. By turning it off, the network works fine and communicate with external properly.

You can turn it off in ‘Preferences’ as shown in the below screenshot.