I have it working but i have re-read documentation and do not see how to do what i need. 

I explain it :)

Now i have only one LCR provider and i need to add a backup one.

I do not know if its enough to add under same lcr_id or its better to add with different one and add several lcr_rule and lcr_rule_target 

Acordding to next_gw() function, what is better to be used? In my case. a primary providers is used and only a backup one for the momment.

Thanks for your help

Alberto