I've been tasked with re-writing some sub-par Ansible playbooks to stand up a Cassandra cluster in CentOS. Quite frankly, there doesn't seem to be much information on Cassandra out there.

I've managed to get the service running on all three nodes at the same time, using the following configuration file, info scrubbed.

```
HOSTIP=10.0.0.1
MSIP=10.10.10.10
ADMIN_EMAIL=my@email.com
LICENSE_FILE=/tmp/license.conf
USE_LDAP_REMOTE_HOST=n

ENABLE_AX=y
MP_POD=gateway

REGION=test-1

USE_ZK_CLUSTER=y
ZK_HOSTS="10.0.0.1 10.0.0.2 10.0.0.3"
ZK_CLIENT_HOSTS="10.0.0.1 10.0.0.2 10.0.0.3"

USE_CASS_CLUSTER=y
CASS_HOSTS="10.0.0.1:1,1 10.0.0.2:1,1 10.0.0.3:1,1"
CASS_USERNAME=test
CASS_PASSWORD=test

```

The HOSTIP changes depending on which node the configuration file is on.

The problem is, when I run `nodetool ring`, each node says there's only two nodes in the cluster: itself and one other, seemingly random from the other two.

What are some basic sanity checks to determine a "healthy" Cassandra cluster? Why is nodetool saying each one thinks there's a different node missing from the cluster?