--- a/README.md	Mon Mar 02 21:46:27 2015 +0200
+++ b/README.md	Mon Mar 02 21:47:08 2015 +0200
@@ -191,6 +191,27 @@
         fixed-address 10.2.0.1;
     }
 
+### DHCP subgroups
+Hosts can be assigned to DHCP subgroups by hardware ethernet:
+
+#### `dhcpd.conf`
+    class "test-hosts" {
+        match hardware;
+    }
+
+#### `etc/hosts/dhcp-classes.test`
+    [foo]
+        ethernet        = 00:11:22:33:44:55
+        dhcp:subclass   = test-hosts
+
+#### `bin/pvl.hosts-dhcp etc/hosts/dhcp-classes.test`
+    host foo {
+        option host-name foo;
+        hardware ethernet 00:11:22:33:44:55;
+    }
+
+    subclass "test-hosts" 1:00:11:22:33:44:55;
+
 # `update`
 A script to drive the *pvl.hosts* tools for maintaing a set of zone/host files for a DNS/DHCP server.
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/etc/hosts/dhcp-classes.test	Mon Mar 02 21:47:08 2015 +0200
@@ -0,0 +1,4 @@
+[foo]
+    ethernet        = 00:11:22:33:44:55
+    dhcp:subclass   = test-hosts
+