TCP 2181
Synopsis
- Port 2181/TCP is the default client port for Apache ZooKeeper.
- Apache Kafka (pre-KRaft/KIP-500) connects to ZooKeeper on 2181 for broker coordination (e.g., Confluent Platform 5.x/6.x deployments).
- Apache HBase uses ZooKeeper on 2181 to track region servers and master coordination in Hadoop distributions (Cloudera/Hortonworks).
- Apache SolrCloud relies on ZooKeeper at 2181 for cluster state and configuration management.
- Apache Druid uses ZooKeeper on 2181 for service discovery and leader election.
- Apache Accumulo coordinates via ZooKeeper on 2181.
- ClickHouse can use an external ZooKeeper on 2181 for replication and distributed DDL coordination.
- Apache Mesos masters use ZooKeeper on 2181 for leader election in HA clusters.
- This port is often targeted when ZooKeeper is exposed without authentication, enabling attackers to read/modify znodes and disrupt or take over clusters.
Observed activity
Last 30 days
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