diff --git a/doc/sphinx/arm/dhcp4-srv.rst b/doc/sphinx/arm/dhcp4-srv.rst
index 4fb6bc81279ca4824aeb36396f495a91340da3c0..a366793f57ebdb09ae8a6f4ab71146890bc95946 100644
--- a/doc/sphinx/arm/dhcp4-srv.rst
+++ b/doc/sphinx/arm/dhcp4-srv.rst
@@ -5166,6 +5166,13 @@ configurations, e.g. shared networks. See :ref:`dhcp4-relay-override` for detail
    classification mechanism alters the way in which a subnet is selected
    for the client, depending on the classes to which the client belongs.
 
+.. note::
+
+   Starting with Kea 1.7.9, the order used to find a subnet which matches
+   required conditions to be selected is the ascending subnet identifier
+   order. When the selected subnet is a member of a shared network the
+   whole shared network is selected.
+
 .. _dhcp4-relay-override:
 
 Using a Specific Relay Agent for a Subnet
diff --git a/doc/sphinx/arm/dhcp6-srv.rst b/doc/sphinx/arm/dhcp6-srv.rst
index bcfbed8db2e88f87cd015908bedd10b6616e4a62..073495dd6b5549cbb35b5a6784404d391da3747e 100644
--- a/doc/sphinx/arm/dhcp6-srv.rst
+++ b/doc/sphinx/arm/dhcp6-srv.rst
@@ -4921,6 +4921,16 @@ DHCPv6 server:
 Using a Specific Relay Agent for a Subnet
 =========================================
 
+The DHCPv6 server follows the same principles than in IPv4 to select
+a subnet for the client with noticable differences mainly for relays.
+
+.. note::
+
+   Starting with Kea 1.7.9, the order used to find a subnet which matches
+   required conditions to be selected is the ascending subnet identifier
+   order. When the selected subnet is a member of a shared network the
+   whole shared network is selected.
+
 The relay must have an interface connected to the link on which the
 clients are being configured. Typically the relay has a global IPv6
 address configured on that interface, which belongs to the subnet from