diff --git a/hosts/aluminium/configuration.nix b/hosts/aluminium/configuration.nix
index 7e843b6..cdd652a 100644
--- a/hosts/aluminium/configuration.nix
+++ b/hosts/aluminium/configuration.nix
@@ -74,9 +74,6 @@
         "voice"
       ];
     };
-    firewall.extraForwardRules = ''
-      tcp flags syn tcp option maxseg size set rt mtu
-    '';
     firewall.extraInputRules = ''
       iifname "voice" udp dport 5059 accept
       ip saddr 217.10.68.150 udp dport 5060 accept
@@ -119,6 +116,16 @@
     };
   };
 
+  networking.nftables.tables.pppoe = {
+    family = "ip";
+    content = ''
+      chain clamp {
+        type filter hook forward priority mangle;
+        oifname "ppp0" tcp flags syn tcp option maxseg size set rt mtu comment "clamp MSS to Path MTU"
+      }
+    '';
+  };
+
   zramSwap = {
     enable = true;
     algorithm = "zstd";