Failed to send external multicast response – How to solve related issues

Opster Team

Feb-20, Version: 1.7-8.0

Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.

To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them.

This guide will help you check for common problems that cause the log ” Failed to send external multicast response ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: discovery, discovery-multicast, ping, Plugin and response.

Log Context

Log “failed to send external multicast response” classname is
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

                if (logger.isTraceEnabled()) {
                    logger.trace("sending external ping response {}"; builder.string());
            } catch (Exception e) {
                logger.warn("failed to send external multicast response"; e);

        private void handleNodePingRequest(int id; DiscoveryNode requestingNodeX; ClusterName requestClusterName) {
            if (!pingEnabled || multicastChannel == null) {


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