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 can resolve issues that cause many errors.

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.

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up to analyze Elasticsearch configuration and help resolve this error.

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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