diff --git a/lib.nix b/lib.nix
index b9a0406..6196a81 100644
--- a/lib.nix
+++ b/lib.nix
@@ -57,8 +57,17 @@ let
   getHostGatewayV6 = hostname:
     getSiteGatewayV6 entities.hosts."${hostname}".site;
 
+  getSiteNetwork = siteName: entities.sites."${siteName}".network;
+
+  getSiteV4PrefixLength = siteName:
+    toInt (elemAt (splitString "/" (getSiteNetwork siteName)));
+
+  getSiteV6PrefixLength = siteName:
+    abort "not implemented: getSiteV6PrefixLength";
+
 in {
   inherit getHostSite getHostDomain getHostRealm getHostFqdn getHostIpv4
     getHostIpv6 getHostIps getDomainPostgresqlServer getSiteHosts getDomainHosts
-    getSiteGatewayV4 getHostGatewayV4 getSiteGatewayV6 getHostGatewayV6;
+    getSiteGatewayV4 getHostGatewayV4 getSiteGatewayV6 getHostGatewayV6
+    getSiteV4PrefixLength getSiteV6PrefixLength;
 }