anchor.diff:              iptables -t nat -F POSTROUTING
             '';
         };
  -
     };
  -
   }
  
positive.code:     };
  
      networking.nat.internalIPs = mkOption {
        example = "192.168.1.0/24";
        description =
          ''
            The IP address range for which to perform NAT.  Packets
            coming from these addresses and destined for the external
            interface will be rewritten.
          '';
      };
  
negative.code: # This module enables Network Address Translation (NAT).
  # XXX: todo: support multiple upstream links
  # see http://yesican.chsoft.biz/lartc/MultihomedLinuxNetworking.html
  
  { config, pkgs, ... }:
  
  