diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index c04431144f7ab9610d019f598a6b104c5c3e42f3..2572eecc3e86a1eb8cbb96fb47c94a014186e7af 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -25,7 +25,8 @@ ip_default_ttl - INTEGER
 ip_no_pmtu_disc - INTEGER
 	Disable Path MTU Discovery. If enabled in mode 1 and a
 	fragmentation-required ICMP is received, the PMTU to this
-	destination will be set to min_pmtu (see below). You will need
+	destination will be set to the smallest of the old MTU to
+	this destination and min_pmtu (see below). You will need
 	to raise min_pmtu to the smallest interface MTU on your system
 	manually if you want to avoid locally generated fragments.
 
@@ -49,7 +50,8 @@ ip_no_pmtu_disc - INTEGER
 	Default: FALSE
 
 min_pmtu - INTEGER
-	default 552 - minimum discovered Path MTU
+	default 552 - minimum Path MTU. Unless this is changed mannually,
+	each cached pmtu will never be lower than this setting.
 
 ip_forward_use_pmtu - BOOLEAN
 	By default we don't trust protocol path MTUs while forwarding