VirtualBox multicast on a bridged network

Question

using VirtualBox, I got two guests (DEBIAN7.7) on my host (WINDOWS7). Each of the two guests has a bridge network interface, eth1 and can ping the other one, I can see each eth1 has multicast enabled. Everything looks fine but, multicast itself seems not working. How can I check if the bridge obtained network support multicast? How to set VirtualBox guests network supporting multicast?

UPDATE: given guests's ip address as 192.168.0.9 and 192.168.0.10, tcpdump -i eth1 -n src host 192.168.0.10 shows that very packets were sent from guest. I got a Wildfly on each guest which is supposed to go in cluster.

UPDATE: digging deeper into issue, I can see Wildfly istances go cluster (... Received new cluster view: [srv2/web|3] (2) [srv2/web, srv1/web]) but they don't share http session. Weird.

Solution

I can confirm that multicast does work between two VirtualBox (v4.3.20) VMs using bridged networking. I used the open-mtools package to test the traffic, along with Wireshark on the host. Here is a sample test:

From VM1 (Receiver):

mdump -omdump1.log 224.9.10.11 12965

From VM2 (Sender):

msend -1 224.9.10.11 12965 15 

Comments

[heavyd]

How are you testing your multicast packets? In order to receive multicast traffic the client must join the multicast group that the multicast traffic is sent to, otherwise it will never receive the traffic.

[Francesco]

@heavyd I'm a newbie at Linux. I can see both Wildfly instances connect to the same multicast address but they don't go cluster. Any tip to check if multicast is supported are welcome.

[Francesco]

hello, I tried with netcat: netcat -l 230.0.0.4 on a node and echo "hi" | netcat 230.0.0.4 45688 on the other node of the cluster. 230.0.0.4:45688 is the JGroups udp multicast address used by Wildfly nodes. I get back a Network is unreachable. What am I missing? TIA.

[heavyd]

First off, I'm pretty sure netcat uses TCP by default, you'll need the -u option to make it use UDP, as multicast doesn't work over TCP. Also, I don't think netcat will join the multicast group when listening with the command line you gave.

[Francesco]

having some problem making open-mtools work. Can you point me to some documentations about it?

[Francesco]

I made some tests using jgroups. On a guest I execute java -classpath org.jgroups.tests.McastReceiverTest -mcast_addr ... -port ... and on the other guest I execute java -classpath org.jgroups.tests.McastSenderTest -mcast_addr ... -port .... I can send some data and receive correctly on this addresses 230.0.0.4:45688, 230.0.0.4:45700 and 224.0.1.105:23364. It looks multicast is working. Problem persists but you point me to the right direction.