diff --git a/nix/lib/config/options.nix b/nix/lib/config/options.nix
index 7ef6f47..8ace91b 100644
--- a/nix/lib/config/options.nix
+++ b/nix/lib/config/options.nix
@@ -155,7 +155,11 @@ let
       };
       isRouter = mkOption {
         type = types.bool;
-        default = config.site.hosts.${name}.interfaces ? core;
+        # isRouter = Part of the core network?
+        default =
+          config.site.hosts.${name}.interfaces ? core &&
+          config.site.net.core.hosts4 ? name;
+        description = "Should this host route?";
       };
       forwardPorts = mkOption {
         type = with types; listOf (submodule { options = {