diff --git a/system/hosts/router/default.nix b/system/hosts/router/default.nix
index b1a1f23..9043c21 100644
--- a/system/hosts/router/default.nix
+++ b/system/hosts/router/default.nix
@@ -282,6 +282,7 @@ in {
   ];
   router-settings.dhcp6Reservations = [
     { ipAddress = serverAddress6;
+      duid = cfg.serverDuid;
       macAddress = cfg.serverMac; }
     { ipAddress = vacuumAddress6;
       macAddress = cfg.vacuumMac; }
@@ -434,11 +435,11 @@ in {
       gateways = [ netAddresses.lan6 ];
       radvdSettings.AdvAutonomous = true;
       coreradSettings.autonomous = true;
-      # don't autoallocate addresses, keep autonomous ones
+      # don't allocate addresses for most devices
       keaSettings.pools = [ ];
       # just assign the reservations
-      keaSettings.reservations = map (res: {
-        hw-address = res.macAddress;
+      keaSettings.reservations = map (res:
+      (if res.duid != null then { duid = res.duid; } else { hw-address = res.macAddress; }) // {
         ip-addresses = [ res.ipAddress ];
       }) cfg.dhcp6Reservations;
     });
diff --git a/system/hosts/router/options.nix b/system/hosts/router/options.nix
index 023614b..2b6d736 100644
--- a/system/hosts/router/options.nix
+++ b/system/hosts/router/options.nix
@@ -13,6 +13,11 @@
       description = "server's mac address";
       type = lib.types.str;
     };
+    serverDuid = lib.mkOption {
+      description = "server's duid";
+      type = with lib.types; nullOr str;
+      default = null;
+    };
     serverInitrdMac = lib.mkOption {
       description = "server's mac address in initrd";
       type = lib.types.str;
@@ -92,9 +97,15 @@
           description = "device's ip address";
         };
         options.macAddress = lib.mkOption {
-          type = lib.types.str;
+          type = with lib.types; nullOr str;
+          default = null;
           description = "device's mac address";
         };
+        options.duid = lib.mkOption {
+          type = with lib.types; nullOr str;
+          default = null;
+          description = "device's duid";
+        };
       });
     };
     dnatRules = lib.mkOption {