Cassandra Cluster (different DataCenters and Hetzner private IP)

Workaround for Cassandra Cluster with nodes in different DataCenters where Hetzner with private IP is one of these DC:

0) Open firewalld ports 9042/tcp 7000/tcp

1) DC names in /etc/cassandra/conf/cassandra-rackdc.properties must be different

2) hostname returns right host name (check hostname -A, etc.)

3) Don't forget about sudo rm -rf /var/lib/cassandra/data/system/*

4) endpoint_snitch: GossipingPropertyFileSnitch

5) ## listen_address in Hetzner DC is commented. So Node takes its public IP

6) rpc....

7) broadcast....

8) For seeds in both Nodes we point only one (in this particular case - RU) DC IP

based on https://docs.datastax.com/en/cassandra/3.0/cassandra/initialize/initMultipleDS.html