def gateway_address pool = "default"
      address = addresses.select{|a| a.pool == pool}.map{|a| a.gateway}.first
      return address if address
      if addresses.length > 0 then
        addresses.first.gateway
      else
        nil
      end
    end
def gateway_address pool = "default"
      address = addresses.select{|a| a.pool == pool}.map{|a| a.gateway}.first
      return address if address
      if addresses.length > 0 then
        addresses.first.gateway
      else
        nil
      end
    end
Return the gateway address for the specified pool, or the first gateway
 @note If there is no address in the specified pool, the gateway of the first usable address is
 used, which may not be desired.
 @param [String] pool The address pool to find a gateway on
 @return [String] Gateway address, or nil