diff --git a/hosts/neptun/configuration.nix b/hosts/neptun/configuration.nix
index 8ac3d1a..ec06d6b 100644
--- a/hosts/neptun/configuration.nix
+++ b/hosts/neptun/configuration.nix
@@ -42,6 +42,12 @@
   #   default via fe80::1 dev eth0 metric 1024 onlink
   networking.defaultGateway6 = { address = "fe80::1"; interface = "eth0"; };
   networking.nameservers = [ "9.9.9.9" "1.1.1.1" "2620:fe::fe" ];
+  # Addressing is fully static above, but netcup's router still sends periodic
+  # RAs on this segment; the kernel then tries (and fails, since the static
+  # route already exists) to install its own default route from them, spamming
+  # "ndisc_router_discovery failed to add default route" on the console. Stop
+  # it from processing RAs on eth0 at all rather than just live with the noise.
+  boot.kernel.sysctl."net.ipv6.conf.eth0.accept_ra" = 0;
 
   # ---- Local split-DNS stub ----
   # neptun must NOT take the tailnet's DNS: headscale points every node at