diff --git a/docs/reference/docs/index_.asciidoc b/docs/reference/docs/index_.asciidoc
index bfb6dad35d5..01ce382e965 100644
--- a/docs/reference/docs/index_.asciidoc
+++ b/docs/reference/docs/index_.asciidoc
@@ -359,6 +359,11 @@ place in the background, set the `replication` parameter to `async`.
 When asynchronous replication is used, the index operation will return
 as soon as the operation succeeds on the primary shard.
 
+The default value for the `replication` setting is `sync` and this default can 
+be overridden on a node-by-node basis using the `action.replication_type`
+setting. Valid values for replication type are `sync` and `async`. To alter this
+behavior per-operation, the `replication` request parameter can be used.
+
 [float]
 [[index-refresh]]
 === Refresh