diff --git a/system/options.nix b/system/options.nix
index 81e4ec9efbf..bc694312231 100644
--- a/system/options.nix
+++ b/system/options.nix
@@ -310,6 +310,29 @@
   }
 
 
+  {
+    name = ["networking" "interfaceMonitor" "enable"];
+    default = false;
+    description = "
+      If <literal>true</literal>, monitor Ethernet interfaces for
+      cables being plugged in or unplugged.  When this occurs, the
+      <optional>dhclient</optional> service is restarted to
+      automatically obtain a new IP address.  This is useful for
+      roaming users (laptops).
+    ";
+  }
+
+
+  {
+    name = ["networking" "interfaceMonitor" "beep"];
+    default = false;
+    description = "
+      If <literal>true</literal>, beep when an Ethernet cable is
+      plugged in or unplugged.
+    ";
+  }
+
+
   {
     name = ["fileSystems"];
     default = [];
diff --git a/upstart-jobs/default.nix b/upstart-jobs/default.nix
index f1e0a2e959f..f74fedcce1e 100644
--- a/upstart-jobs/default.nix
+++ b/upstart-jobs/default.nix
@@ -119,6 +119,13 @@ import ../upstart-jobs/gather.nix {
       interfaces = config.get ["networking" "interfaces"];
     })
 
+  # ifplugd daemon for monitoring Ethernet cables.
+  ++ optional ["networking" "interfaceMonitor" "enable"]
+    (import ../upstart-jobs/ifplugd.nix {
+      inherit (pkgs) ifplugd writeScript bash;
+      inherit config;
+    })
+
   # DHCP server.
   ++ optional ["services" "dhcpd" "enable"]
     (import ../upstart-jobs/dhcpd.nix {
diff --git a/upstart-jobs/dhclient.nix b/upstart-jobs/dhclient.nix
index f2ebc39190d..3f198d44d2d 100644
--- a/upstart-jobs/dhclient.nix
+++ b/upstart-jobs/dhclient.nix
@@ -12,6 +12,8 @@ in
 
 {
   name = "dhclient";
+
+  extraPath = [dhcp];
   
   job = "
 description \"DHCP client\"
diff --git a/upstart-jobs/ifplugd.nix b/upstart-jobs/ifplugd.nix
new file mode 100644
index 00000000000..b3f4b811c33
--- /dev/null
+++ b/upstart-jobs/ifplugd.nix
@@ -0,0 +1,34 @@
+{ifplugd, config, writeScript, bash}:
+
+let
+
+  # The ifplugd action script, which is called whenever the link
+  # status changes (i.e., a cable is plugged in or unplugged).  We do
+  # nothing when a cable is unplugged.  When a cable is plugged in, we
+  # restart dhclient, which will hopefully give us a new IP address
+  # if appropriate.
+  plugScript = writeScript "ifplugd.action" "#! ${bash}/bin/sh
+    if test \"$2\" = up; then
+      initctl stop dhclient
+      initctl start dhclient
+    fi
+  ";
+
+in 
+
+{
+  name = "ifplugd";
+
+  extraPath = [ifplugd];
+  
+  job = "
+description \"Network interface connectivity monitor\"
+
+start on network-interfaces/started
+stop on network-interfaces/stop
+
+respawn ${ifplugd}/sbin/ifplugd --no-daemon --no-startup --no-shutdown \\
+    ${if config.get ["networking" "interfaceMonitor" "beep"] then "" else "--no-beep"} \\
+    --run ${plugScript}";
+  
+}