HA Failover question

hello ereryone Encountered a problem,please help me take a look. bigip1.com and bigip2.com build HA ,the failover are ha address and internal address,bigip1.com is active and bigip2.com is standby; now pull out HA interface , I found bigip1.com is active ,bigip2.com is also active ; when I pull out internal interface ,I found bigip1.com is active ,bigip2.com is also standby . not understand why ;I think failover have two Judge conditions,only two judge conditions not work ,the two bigip equipments to be active all ;