Docker swarm preferred node?

Question

Docker

Hello!
I'm running nginx on a docker swarm cluster. I have 2 nodes where vrrp is configured. At the moment I have 2 replicas running and nginx is on both nodes. But in order not to drive extra traffic (I have php and so on after nginx), I would like to run nginx only on the node to which the external ip is currently attached, and if this node falls, so that nginx would move to the second one. How to fix the preferred node on which nginx will be by default... Or am I missing something? :)