diff --git a/doc/manuals/chapters/configuration.adoc b/doc/manuals/chapters/configuration.adoc
index f61fd55..fd2d7ed 100644
--- a/doc/manuals/chapters/configuration.adoc
+++ b/doc/manuals/chapters/configuration.adoc
@@ -338,3 +338,21 @@
 sgsn
  no compression v42bis
 ----
+
+=== Encryption
+
+Encryption can be enabled if the auth-policy is set to remote and the
+HLR subscriber entries contain the keys of the SIM card. See
+<<sgsn-ex-gsup>> on how to connect to an external HLR.
+
+.Example: Turn on encryption (GEA3)
+----
+sgsn
+ encryption GEA3
+----
+
+.Example: Turn off encryption (GEA0)
+----
+sgsn
+ encryption GEA0
+----
