anchor.diff:      options = {
         ip = mkOption {
           type = types.str;
  -        default = "${netPrefix}${genByte name 0}.${genByte name 3}";
  +        default = "10.@subnet@.${genByte name 0}.${genByte name 3}";
         };
   
         mac = mkOption {
  
positive.code:   genByte = s: n: toString (hexByteToInt (
      substring n 2 (mkMAC s)
    ));
  
    netPrefix = "10.${genByte cfg.name 0}.";
  
    instanceOpts = { name, config, lib, ... }: {
      imports = [
  
negative.code:       <name>net-@testid@</name>
        <bridge name="virbr-@testid@" stp="off"/>
        <domain name="${cfg.domain}" localOnly="yes"/>
        <ip address="10.@subnet@.0.1" netmask="255.255.0.0">
          <dhcp>
            <range start="10.@subnet@.0.2" end="10.@subnet@.255.254" />
            ${concatStrings (mapAttrsToList (name: i: ''
              <host mac="${i.mac}" name="${name}" ip="${i.ip}"/>
            '') cfg.instances)}
  