23.6.3. JGroups Troubleshooting

23.6.3.1. Nodes do not form a cluster

Ensure that your machine is set up correctly for IP multicast. There are two test programs that can detect this: McastReceiverTest and McastSenderTest.

Start McastReceiverTest from the $JBOSS_HOME/server/production/lib directory, like so:

java -cp jgroups.jar org.jgroups.tests.McastReceiverTest -mcast_addr 224.10.10.10 -port 5555

In another window, start McastSenderTest from the same directory:
```
java -cp jgroups.jar org.jgroups.tests.McastSenderTest -mcast_addr 224.10.10.10 -port 5555
```
Note
Use the -bind_addr switch to bind to a specific network interface card (NIC). To bind to an NIC with an IP address of 192.168.0.2, you would use -bind_addr 192.168.0.2. This parameter can be used in both senders and receivers.
Type in the McastSenderTest window. You should be able to see the output in the McastReceiverTest window.

If you cannot, try using -ttl 32 in the sender. If this still fails, consult a system administrator to help you set up IP multicast correctly. Check that multicast will work on the interface you have chosen. If the machines have multiple interfaces, ask which interface is correct for multicasting.

When multicast is working correctly on each machine in your cluster, verify that your network is working correctly by repeating this test with McastReceiverTest on one machine and McastSenderTest on another.