The Splunk universal forwarder now supports IPv6 with IPv4/IPv6 DualStack networking functionality. If you are using IPv6 DualStack networking in your configuration, add connectUsingIpVersion = 6-only to the [general] stanza in [server.conf|server.conf] on the universal forwarder so that splunkd will attempt to connect to the IPv6 address. To enable IPv6 addresses with DualStack networking, see https://lantern.splunk.com/Splunk_Platform/Product_Tips/Administration/Splunk_over_IPv6_Runbook_for_Splunk_Enterprise_Customers for more information.