On Wed, Nov 16, 2016 at 05:24:36PM +0000, Corey Melanson wrote: > Please let me know if there is any other information that would be helpful. > > Thank you, > Corey Hi Corey, I tried to reproduce your issue in a similar VM setup, but was unsuccessful so far. For me things seem to work with 4.9-rc3 kernels. What I tried: [vm-s] -- [vm-br] == [vm-r] vm-s and vm-br are connected via one interface pair. vm-br and vm-r share two interfaces. On vm-r's 1st interface there is socat running which joins 239.236.15.150 [1]. On vm-r's 2nd interface there is a tcpdump listening for UDP packets. -> vm-br with a "bridge mdb show dev br0" shows one entry for 239.236.15.150 for the 1st interface towards vm-r vm-s sends multicast traffic to 239.236.15.150 via socat [2]. -> Is received successfully in socat on vm-r, tcpdump on 2nd interface stays empty Then I did not do the full interface hotplugging, but instead typed your "bridge mdb add..." command on vm-br for the 2nd interface towards vm-r. Finally I redid the socat transmission on vm-s. And vm-r received this packet successfully both in socat running on its 1st interface and in tcpdump running on its 2nd one. Could you retry with a recent kernel, too, Corey? Regards, Linus [1]: $ socat -u UDP4-RECV:1234,reuseaddr,ip-add-membership="239.236.15.150:ens3" - [2]: $ socat - UDP4-DATAGRAM:"239.236.15.150:1234"