I set up a multi-DC cassandra nodes in HP Cloud. I have 4 nodes in AZ2, 4 nodes in AZ3, and set up a opscenter in AZ2. As one thread says, the interface in /etc/opscenter/opscenterd.conf should be reachable by other nodes, since I have nodes in another DC (AZ3), I set the public IP. I saw the error in opscenter.log. Apparently, it's not a successful bind.
twisted.internet.error.CannotListenError: Couldn't listen on 126.96.36.199:8888: [Errno 99] Cannot assign requested address.
I also tried private IP. No agents on cassandra nodes are able to talk to it, even in the same DC. opscenter shows 0 of 8 agents found. I tried to install agents from opscenter, no luck either.