def find_and_route_public_block(gateway_ip)
      num_devices = @environment.non_gateway_devices.length
      prefix = CIDR.smallest_prefix(num_devices)
      public_block =
        PublicIpBlock.find_and_route_block_to_public_ip_address(gateway_ip, prefix)
      public_block.reserve_to(gateway_ip.network_device)
      public_block
    end


then here  I will try to delete it

def make_assignments(net_device_block, ex_net_zone)
        @environment = SimpleConfig::Environment.create(@owner, @gateway,
                                                        @devices, @alias_name,
                                                        ex_net_zone.zone)
        gateway_ip = net_device_block.assign_gateway_ip
        ip_blocks = SimpleConfig::IpBlocks.new(@private_cidr, environment)
        public_block = ip_blocks.find_and_route_public_block(gateway_ip)
        ActiveRecord::Base.transaction do
          private_block = ip_blocks.create_private_block
          public_block.nat_to(private_block)
          ip_blocks.allocate_ips_to_devices(public_block, private_block)
          SimpleConfig::ServiceNet.assign(@devices, @owner)
          SimpleConfig::Vlan.create(@vlan_segment_name,
                                    environment,
                                    private_block,
                                    ex_net_zone.zone)
          environment.reload
        end
      rescue => e
        remove_devices = @devices.map{ |d| d.destroy} #"destroy the network devices in the environment"
        remove_environment = @environment.network_environment.destroy #"destroy the environment"
        remove_gateway_ip = gateway_ip.hard_deallocate! #"destroy the gateway's IP"
        remove_public_ip_block = public_block.destroy #"destroy the good block"
    end