7000 Cassandra-internode TCP
Reference for TCP port 7000, commonly associated with Cassandra-internode.
What it's for
Port 7000 is the default port for internode communication within an Apache Cassandra cluster — the traffic nodes use to replicate data between each other, gossip cluster state, and coordinate distributed operations. Application clients don't connect here directly; this is purely internal cluster traffic.
Protocol basics
Internode communication runs over TCP using Cassandra's own internal binary protocol, distinct from the CQL native protocol clients use on port 9042. This traffic includes gossip (nodes periodically exchanging state information about the cluster's health and topology) and the actual data replication/streaming that happens as writes propagate across replica nodes according to the keyspace's replication strategy. Since this port carries genuine application data between nodes, it should be restricted to the cluster's own private network, never exposed externally.