Reason for dockerd error: "...memberlist: failed to receive: Remote state is encrypted and encryption is not configured from=<ip>:<port>"

when experimenting on 3 hosts with Overlay Networks with Swarmmode and I get strange log entries which are nowhere explained, like this:

dockerd[8208]: time=“2019-05-31T08:33:14.582202133Z” level=error msg="2019/05/31 08:33:14 [ERR] memberlist: failed to receive: Remote state is encrypted and encryption is not configured from=:54192

Forming a Swarm works, but even ingress overlay network is not propagated properly to the other nodes.

Is there anything I can check about Docker/Swarm encryption configuration ? If it is not the gossip communication being the probelem (as nodes can join and are seen with docker node ls), what kind of comms are are meant with the log entry ?

Peter


Docker Version: 17.09.1-ce
Docker API version: 1.32