{
         rr_list_t answers_list = fill_answers_list( HostDnsAddress, NameServer);
 
-        int resolved_ip_count = answers_list.size();
+        size_t resolved_ip_count = answers_list.size();
         if ( resolved_ip_count < 1 )
         {
             GlobalLogger.error() << "Error: host "
 
 rr_list_t DnsResolver::fill_answers_list(
         const string &host_dns_address,
-        const string &name_server)
+        const string &name_server
+) const
 {
     BOOST_ASSERT( !host_dns_address.empty() );
     BOOST_ASSERT( !name_server.empty() );
 void DnsResolver::fill_resolved_ip_list(
         const rr_list_t& answers_list,
         list<HostAddress> *resolved_host_address_list
-)
+) const
 {
     BOOST_ASSERT( 1 <= answers_list.size() );
     BOOST_ASSERT( resolved_host_address_list != NULL );
             a_resource *a_rr = dynamic_cast<a_resource *> (
                     resource_record.get()
             );
-            string ip = a_rr->address().to_string();
-            int ttl = a_rr->ttl();
+            if ( a_rr != NULL )
+            {
+                string current_ip = a_rr->address().to_string();
+                uint32_t current_ttl = a_rr->ttl();
 
-            HostAddress resolved_host( ip, ttl );
-            resolved_host_address_list->push_back( resolved_host );
+                HostAddress resolved_host( current_ip, current_ttl );
+                resolved_host_address_list->push_back( resolved_host );
 
-            GlobalLogger.info() << "- " << ip
-                    << " [" << ttl << "s]" << endl;
+                GlobalLogger.info() << "- " << current_ip
+                        << " [" << current_ttl << "s]" << endl;
+            }
         }
     }
 
 
     boost::net::dns::rr_list_t fill_answers_list(
             const std::string &host_dns_address,
             const std::string &name_server
-    );
+    ) const;
     void fill_resolved_ip_list(
             const boost::net::dns::rr_list_t& answers_list,
             std::list<HostAddress> *resolved_host_address_list
-    );
+    ) const;
 
 private:
     /// The list of IPs available to the host DNS.