Multicast with Docker Swarm and overlay network

Question

I am testing an application using multicast for the discovery. I created a Swarm cluster and a network create -d overlay swarm-net so the containers share the same LAN across the several Swarm agents hosts.

The discovery seemed to not be working, so I installed tshark. tshark shows the IP address node within which tshark is running and the multicast address for the packet being sent though tshark does not show any incoming multicast packet.

Note that, as I don't know a better way to do so, the container is run with --privileged to enable tshark. Note also that containers can communicate with each other.

Is the multicast blocked because of Docker iptable? How to enable multicast in an overlay network?

Answer 1

Overlay-driver network does not support multicast as it uses vxlan unicast, according to chanwit (and my experience so far).

Note that the plugin weave net (an overlay network driver) does support multicast!