Redis requires the following TCP port to be accessible:

• 6379: Client-server connections
• 16379: Node-to-node cluster bus protocol

Redis in a single node setup will only use port 6379 (by default). On the other hand, Redis Cluster will use a port offset of + 10000 from its client port for node-to-node communication. Assuming the default configuration, this would also require the opening of port 16379. In a non-default port configuration for Redis Cluster, be sure to open both the client port as well as client port + 10000.