10 minutes delay in executing the first query from some ips

[Antonio BM]

I have installed mysql server 5.6.25 in debian 7 server.
When I connect from some external ips, I have 10 minutes delay in executing the first query. Then I can run any query and have no extra delay. Only it applies to the first query and from some ips.
I try adding skip-host-cache and skip-name-resolve to my.cnf, but not fix.
Reverse-Dns problem could be?
I could modify the host and resolve.cnf file from server.
Any suggestions?
Thanks in advance.

These are log and my.cnf file

150911 9:41:20 165 Connect [e-mail] on database_name
165 Query /* mysql-connector-java-5.1.6 ( Revision: ${svn.Revision} ) */SHOW VARIABLES WHERE Variable_name ='language' OR Variable_name = 'net_write_timeout' OR Variable_name = 'interactive_timeout' OR Variable_name = 'wait_timeout' OR Variable_name = 'character_set_client' OR Variable_name = 'character_set_connection' OR Variable_name = 'character_set' OR Variable_name = 'character_set_server' OR Variable_name = 'tx_isolation' OR Variable_name = 'transaction_isolation' OR Variable_name = 'character_set_results' OR Variable_name = 'timezone' OR Variable_name = 'time_zone' OR Variable_name = 'system_time_zone' OR Variable_name = 'lower_case_table_names' OR Variable_name = 'max_allowed_packet' OR Variable_name = 'net_buffer_length' OR Variable_name = 'sql_mode' OR Variable_name = 'query_cache_type' OR Variable_name = 'query_cache_size' OR Variable_name = 'init_connect'
165 Query SHOW COLLATION
165 Query SET NAMES latin1
165 Query SET character_set_results = NULL
165 Query SET autocommit=1
165 Query SELECT curdate() AS fecha, curtime() AS hora

150911 9:50:32 165 Query SELECT * FROM lval WHERE tipo = 'VERSION'

MY.CNF

[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock

[mysqld_safe]
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
nice = 0

[mysqld]
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
lc-messages-dir = /usr/share/mysql
explicit_defaults_for_timestamp

# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
#bind-address = 127.0.0.1

log-error = /var/log/mysql/error.log

# Recommended in standard MySQL setup
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0

#Cambios mios
[mysqld]
skip-host-cache
skip-name-resolve

net_read_timeout=600
net_write_timeout=900

key_buffer_size = 512M
max_allowed_packet = 1024M
thread_stack = 256K
thread_cache_size = 30

max_connections = 300

wait_timeout=86400
interactive_timeout=86400

max_connect_errors = 1000000

query_cache_limit = 128M
query_cache_size = 1024M

general_log_file = /var/log/mysql/mysql.log
general_log = 1
log_warnings = 1
long_query_time = 5
#log-queries-not-using-indexes
expire_logs_days = 10
max_binlog_size = 100M

[mysqldump]
quick
quote-names
max_allowed_packet = 1024M


# * IMPORTANT: Additional settings that can override those from this file!
# The files must end with '.cnf', otherwise they'll be ignored.
#
!includedir /etc/mysql/conf.d/