Understanding Redis Cluster Node IDs and Their Fields

In a Redis cluster, each node is assigned a unique identifier (ID) when it starts, which is used to locate and identify that node within the cluster.

This ID never changes, even if the machine's IP address changes; it is only regenerated if the configuration is deleted or the cluster reset command is executed.

Besides the ID, each node maintains other useful information such as its IP address and port, a set of flags, master information, ping timestamps, connection state, and the slots it holds.

For example, running the cluster nodes command on a local machine produces output like the following:

c2da779de9d436789ed3b89d3be2b97bf0140a54 127.0.0.1:7002@17002 master - 0 1745072596683 3 connected 10923-16383
2a05e263ac4d160c1a7b80da1c231620d2e98b8d 127.0.0.1:7004@17004 slave 0 d4b6c0547293937f33ed9f04cbbc674d39fa058 0 1745072595563 1 connected
0d4b6c0547293937f33ed9f04cbbc674d39fa058 127.0.0.1:7000@17000 myself,master - 0 1745072594000 1 connected 0-5460
7c9a28287ce035fa432db886252aaed35bea37cc 127.0.0.1:7001@17001 master - 0 1745072595563 2 connected 5461-10922
5897121739e7090ca6e6332a423e54a800857abb 127.0.0.1:7005@17005 slave 7c9a28287ce035fa432db886252aaed35bea37cc 0 1745072595665 2 connected
1cb32ba274c3a938098685f16964e331c238c44f 127.0.0.1:7003@17003 slave c2da779de9d436789ed3b89d3be2b97bf0140a54 0 1745072597597 3 connected

Each line contains the following fields:

<id> <ip:port@cport> [<hostname>] <flags> <master> <ping-sent> <pong-recv> <config-epoch> <link-state> <slot> [<slot> ...]

The meaning of each field is:

id : 40‑character globally unique node identifier, set at creation and never changes.

ip:port@cport : The node’s IP address and client port, followed by the cluster bus port.

flags : Comma‑separated node flags such as myself, master, slave, etc.

master : If the node is a replica, this field holds the ID of its master; otherwise it is “-”.

ping-sent : Unix timestamp (ms) of the last ping sent; 0 if none.

pong-recv : Unix timestamp (ms) of the last pong received.

config-epoch : Configuration epoch number used for failover.

link-state : Connection state to the cluster bus, either connected or disconnected.

slot : The hash slots owned by the node, expressed as single numbers or ranges.

Knowing these details helps you monitor node health more effectively and can be a valuable talking point in technical interviews.