Updating production guide with information about switching from ipv4 to ipv6

pedroigor · abstractj · commit cf249fc6aed4 · 2022-08-05T11:55:09.000-03:00
Closes keycloak#11979
diff --git a/docs/guides/src/main/server/configuration-production.adoc b/docs/guides/src/main/server/configuration-production.adoc
@@ -36,4 +36,19 @@ Keycloak runs on top of JGroups and Infinispan, which provide a reliable, high-a
 
 To find out more about using multiple nodes, the different caches and an appropriate stack for your environment, see the <@links.server id="caching"/> guide.
 
+== Configure Keycloak Server with IPv6 or IPv4
+
+The system properties `java.net.preferIPv4Stack` and `java.net.preferIPv6Addresses` are used to configure the JVM for use with IPv4 or IPv6 addresses.
+
+By default, Keycloak is configured to prefer IPv4 addresses. In order to run with IPv6 addresses,
+you need to specify `java.net.preferIPv4Stack=false` (the JVM default) and `java.net.preferIPv6Addresses=true`.
+The latter ensures that any hostname to IP address conversions always return IPv6 address variants.
+
+These system properties are conveniently set by the `JAVA_OPTS_APPEND` environment variable. For example, to change the IP stack preference from its default of IPv4 to IPv6, set an environment variable as follows:
+
+[source, bash]
+----
+export JAVA_OPTS_APPEND="-Djava.net.preferIPv4Stack=false -Djava.net.preferIPv6Addresses=true"
+----
+
 </@tmpl.guide>
