BackEnd administration with 2 ip lines

[Ixora Team Srl]

Hello to all i am new here i jsut installed prestashop for try it but i have some proble, my company have a load balanced dual wan ..so I have 2 differents ip.
When i go to admin section i can login but if i try to switch to another page he ask to log me agian.
If i switch off the second wan this porblem dont apper.
So i suppose is beacuse my ip change and prestashop have some protection which ask me to login agian.
There is a solution?
Which file i need mdify for solve this problem?

Thanks

EDIT:

I think Ifouns solution
i edit the coockie.php file on isLoggedBack function i have comment this part

AND (!isset([s]this->_content['remote_addr']) OR [s]this->_content['remote_addr'] == ip2long([s]_SERVER['REMOTE_ADDR']))

there iwll be some problem if i do that?
thanks