have a two WAN ports in RB951 Router

Hi, i have RB951 Router and i wanted to have Two WAN ports for failover. i made it, Now i have WAN1 (main ISP) and WAN2 (secondary ISP) ports, when i get a cable form WAN1, WAN2 cable is working fine, but i suddenly discovery that when WAN1 ISP side falling down, failover not working, i must get cable form port WAN1 and than WAN2 works fine, can you help me? i need not to get cable form port and failover working automaticaly thanks

Verify your default routes if you have check-gateway=ping enabled. If not, interface link state is the only indicator for your router.
-Chris

post your config
/export hide=sensitive file=yourconfigjul2