machines/nixos/vault01/networking.nix

@@ -58,7 +58,10 @@ let
             LinkLocalAddressing = "no";
             DHCPServer = "yes";
           };
-          linkConfig.Promiscuous = true;
+          linkConfig = {
+            Promiscuous = true;
+            MTUBytes = 1500;
+          };
           addresses = [
             {
               Address = "${servIP}/27";
@@ -134,7 +137,10 @@ let
       Id = 2001;
       address = [ "10.0.254.1/24" ];
 
-      extraNetwork.networkConfig.DHCPServer = "yes";
+      extraNetwork = {
+        networkConfig.DHCPServer = "yes";
+        linkConfig.MTUBytes = 1500;
+      };
     };
   } // builtins.listToAttrs (map mkUserVlan userVlans);
 in
@@ -176,6 +182,7 @@ in
             IPv6AcceptRA = false;
             IPv6SendRA = false;
           };
+          linkConfig.MTUBytes = 1504;
         };
         "50-gretap1" = {
           name = "gretap1";