diff --git a/config/host-config/clunk.nix b/config/host-config/clunk.nix
index 5cd326f..386622a 100644
--- a/config/host-config/clunk.nix
+++ b/config/host-config/clunk.nix
@@ -6,9 +6,7 @@ let
 
   dns-proxy-port = 5335;
 
-  host-packages = with pkgs; [
-    nixops
-  ];
+  host-packages = with pkgs; [ nixops ];
 
   site-name = config.fudo.hosts.${config.instance.hostname}.site;
   site = config.fudo.site.${site-name};
@@ -53,13 +51,9 @@ in {
     network-definition = config.fudo.networks."rus.selby.ca";
   };
 
-  networking = {
-    firewall = {
-      enable = true;
-      trustedInterfaces = [ "intif0" "docker0" ];
-      allowedTCPPorts = [ 22 ];
-    };
+  fudo.hosts.clunk.external-interfaces = [ "enp1s0" ];
 
+  networking = {
     interfaces = {
       enp1s0.useDHCP = true;
 
diff --git a/config/host-config/lambda.nix b/config/host-config/lambda.nix
index d630aa7..8feb358 100644
--- a/config/host-config/lambda.nix
+++ b/config/host-config/lambda.nix
@@ -5,7 +5,7 @@
   nixpkgs.config.permittedInsecurePackages = [
     "openssh-with-gssapi-8.4p1" # CVE-2021-28041
   ];
-  
+
   fudo.slynk.enable = true;
 
   networking = {
@@ -15,9 +15,7 @@
       enp4s0f0.useDHCP = false;
       enp4s0f1.useDHCP = false;
 
-      intif0 = {
-        useDHCP = true;
-      };
+      intif0 = { useDHCP = true; };
     };
   };
 
diff --git a/config/host-config/limina.nix b/config/host-config/limina.nix
index 9c12b98..5fec051 100644
--- a/config/host-config/limina.nix
+++ b/config/host-config/limina.nix
@@ -21,12 +21,6 @@ in {
     ];
 
     networking = {
-      firewall = {
-        enable = true;
-        trustedInterfaces = [ "intif0" "intif1" "intif2" "lo" ];
-        allowedTCPPorts = [ 22 ];
-      };
-
       interfaces = {
         enp1s0 = { useDHCP = true; };
 
@@ -41,14 +35,20 @@ in {
         intif2 = { useDHCP = false; };
       };
 
+      # FIXME: this should be automatic
+      firewall.trustedInterfaces =
+        [ "intif0" "intif1" "intif2" "lo" "docker0" ];
+
       nat = {
         enable = true;
         externalInterface = "enp1s0";
-        internalInterfaces = [ "intif0" ];
+        internalInterfaces = [ "intif0" "intif1" "intif2" ];
       };
     };
 
     fudo = {
+      hosts.limina.external-interfaces = [ "enp1s0" ];
+
       local-network = {
         enable = true;
         domain = domain-name;
diff --git a/config/hosts/limina.nix b/config/hosts/limina.nix
index 04fb8f6..a85eb41 100644
--- a/config/hosts/limina.nix
+++ b/config/hosts/limina.nix
@@ -13,4 +13,5 @@
   profile = "server";
   ssh-pubkey =
     "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIMqymGZ5dI6ChI1Qx1QfjBo/h0+xFwpRx/wQSDxWQprI";
+  tmp-on-tmpfs = false;
 }
diff --git a/config/hosts/plato.nix b/config/hosts/plato.nix
index 8fa9a6c..16187c2 100644
--- a/config/hosts/plato.nix
+++ b/config/hosts/plato.nix
@@ -16,4 +16,5 @@
   build-pubkeys = [
     "ssh-rsa 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"
   ];
+  tmp-on-tmpfs = false;
 }
diff --git a/config/hosts/pselby-work.nix b/config/hosts/pselby-work.nix
index 9797c0e..c41cec0 100644
--- a/config/hosts/pselby-work.nix
+++ b/config/hosts/pselby-work.nix
@@ -1,3 +1,6 @@
 {
   description = "Google Lenovo work laptop.";
+  site = "seattle";
+  profile = "laptop";
+  domain = "sea.fudo.org";
 }
diff --git a/config/hosts/upstairs-desktop.nix b/config/hosts/upstairs-desktop.nix
index dcf14e8..313b1ce 100644
--- a/config/hosts/upstairs-desktop.nix
+++ b/config/hosts/upstairs-desktop.nix
@@ -10,4 +10,7 @@
   ];
   rp = "niten";
   admin-email = "niten@fudo.org";
+  site = "russell";
+  domain = "rus.selby.ca";
+  profile = "desktop";
 }
diff --git a/config/networks/sea.fudo.org.nix b/config/networks/sea.fudo.org.nix
index f93f390..94032da 100644
--- a/config/networks/sea.fudo.org.nix
+++ b/config/networks/sea.fudo.org.nix
@@ -80,7 +80,7 @@ in {
     };
     lambda = {
       ipv4-address = "10.0.0.11";
-      mac-address = "e8:39:35:2c:38:08";
+      mac-address = "02:f5:fe:8c:22:fe";
     };
     plato = { ipv4-address = "10.0.0.21"; };
     cam-entrance = {
diff --git a/config/profile-config/common.nix b/config/profile-config/common.nix
index f27b7c4..6d387d6 100644
--- a/config/profile-config/common.nix
+++ b/config/profile-config/common.nix
@@ -31,7 +31,7 @@ in {
     };
 
     libdefaults = {
-      allow_weak_crypto = false;
+      allow_weak_crypto = true;
       dns_lookup_kdc = true;
       dns_lookup_realm = true;
       forwardable = true;
@@ -45,7 +45,7 @@ in {
     openssh = {
       enable = true;
       startWhenNeeded = true;
-      # useDns = true;
+      useDns = true;
       permitRootLogin = "prohibit-password";
       extraConfig = ''
         GSSAPIAuthentication yes
@@ -55,10 +55,13 @@ in {
       '';
     };
 
-    fail2ban = {
-      enable = true;
-      bantime-increment.enable = true;
-    };
+    fail2ban =
+      let domain-name = config.fudo.hosts.${config.instance.hostname}.domain;
+      in {
+        enable = config.networking.firewall.enable;
+        bantime-increment.enable = true;
+        ignoreIP = config.fudo.domains.${domain-name}.local-networks;
+      };
 
     xserver = {
       layout = "us";
diff --git a/config/profile-config/server.nix b/config/profile-config/server.nix
index 1b0b130..9cc8bf0 100644
--- a/config/profile-config/server.nix
+++ b/config/profile-config/server.nix
@@ -2,11 +2,7 @@
 
 with lib;
 let
-  serverPackages = with pkgs; [
-    emacs-nox
-    reboot-if-necessary
-    test-config
-  ];
+  serverPackages = with pkgs; [ emacs-nox reboot-if-necessary test-config ];
 
   reboot-if-necessary = pkgs.writeShellScriptBin "reboot-if-necessary" ''
     if [ $# -ne 1 ]; then
@@ -50,9 +46,7 @@ in {
   imports = [ ./common.nix ];
 
   config = {
-    environment = {
-      systemPackages = serverPackages;
-    };
+    environment = { systemPackages = serverPackages; };
 
     system.autoUpgrade.enable = false;
 
@@ -60,8 +54,6 @@ in {
 
     networking.networkmanager.enable = mkForce false;
 
-    boot.tmpOnTmpfs = true;
-
     services = {
       xserver.enable = false;
 
diff --git a/config/sites.nix b/config/sites.nix
index 86c3605..5810243 100644
--- a/config/sites.nix
+++ b/config/sites.nix
@@ -21,6 +21,7 @@
           speed-factor = 2;
         };
       };
+      enable-distributed-builds = true;
       # FIXME: good idea?
       # network-mounts = {
       #   "/mnt/documents" = {
diff --git a/lib/fudo/hosts.nix b/lib/fudo/hosts.nix
index b0993c8..477957e 100644
--- a/lib/fudo/hosts.nix
+++ b/lib/fudo/hosts.nix
@@ -89,6 +89,13 @@ let
         default = null;
       };
 
+      tmp-on-tmpfs = mkOption {
+        type = bool;
+        description =
+          "Use tmpfs for /tmp. Great if you've got enough (>16G) RAM.";
+        default = true;
+      };
+
       enable-gui = mkEnableOption "Install desktop GUI software.";
 
       docker-server = mkEnableOption "Enable Docker on the current host.";
@@ -112,6 +119,12 @@ let
         description = "SSH public keys used to access the build server.";
         default = [ ];
       };
+
+      external-interfaces = mkOption {
+        type = listOf str;
+        description = "A list of interfaces on which to enable the firewall.";
+        default = [ ];
+      };
     };
   };
 
@@ -136,6 +149,7 @@ in {
   in {
     networking = {
       hostName = config.instance.hostname;
+      domain = domain-name;
       nameservers = site.nameservers;
       # This will cause a loop on the gateway itself
       #defaultGateway = site.gateway-v4;
@@ -143,13 +157,33 @@ in {
 
       # Necessary to ensure that Kerberos and Avahi both work. Kerberos needs
       # the fqdn of the host, whereas Avahi wants just the simple hostname.`
-      hosts = { "127.0.0.1" = [ "${hostname}.${domain-name}" "${hostname}" ]; };
+      hosts = {
+        "127.0.0.2" = [ "${hostname}.${domain-name}" "${hostname}" ];
+        "127.0.0.1" = [ "${hostname}.${domain-name}" "${hostname}" ];
+        "::1" = [ "${hostname}.${domain-name}" "${hostname}" ];
+      };
+
+      firewall = {
+        enable = (length host-cfg.external-interfaces) > 0;
+        allowedTCPPorts = [ 22 ];
+      };
+    };
+
+    environment.etc.hosts = mkForce {
+      text = ''
+        127.0.0.1 ${hostname}.${domain-name} ${hostname} localhost
+        127.0.0.2 ${hostname} localhost
+        ::1 ${hostname}.${domain-name} ${hostname} localhost
+      '';
+      user = "root";
+      group = "root";
+      mode = "0444";
     };
 
     nix = mkIf
       (has-build-servers && has-build-keys && site.enable-distributed-builds) {
         buildMachines = mapAttrsToList (hostname: buildOpts: {
-          hostName = "${hostname}.${domain}";
+          hostName = "${hostname}.${domain-name}";
           maxJobs = buildOpts.max-jobs;
           speedFactor = buildOpts.speed-factor;
           supportedFeatures = buildOpts.supported-features;
@@ -172,6 +206,8 @@ in {
       autoPrune.enable = true;
     };
 
+    boot.tmpOnTmpfs = host-cfg.tmp-on-tmpfs;
+
     programs.ssh.knownHosts = let
       keyed-hosts =
         filterAttrs (host: opts: opts.ssh-pubkey != null) config.fudo.hosts;
diff --git a/lib/fudo/hosts/local-network.nix b/lib/fudo/hosts/local-network.nix
index f4d2c70..f2de116 100644
--- a/lib/fudo/hosts/local-network.nix
+++ b/lib/fudo/hosts/local-network.nix
@@ -6,6 +6,7 @@ with lib;
 let
   cfg = config.fudo.hosts.local-network;
 
+  # FIXME: this isn't used, is it?
   gatewayServerOpts = { ... }: {
     options = {
       enable = mkEnableOption "Turn this host into a network gateway.";
diff --git a/lib/fudo/sites.nix b/lib/fudo/sites.nix
index 9389b42..db12e10 100644
--- a/lib/fudo/sites.nix
+++ b/lib/fudo/sites.nix
@@ -133,6 +133,12 @@ let
         description = "User as which to run builds.";
         default = "nix-site-builder";
       };
+
+      local-networks = mkOption {
+        type = listOf str;
+        description = "List of networks to consider local at this site.";
+        default = [ ];
+      };
     };
   };