config balance 'global'
        option state 'on'

config policy_rule 'special_rule'    
        option state 'on' 
        option use_policy 'special_policy'

config interface 'WAN1'
        option enabled '1'
        option balance '1'
        option ref '0'

config interface 'WAN5'
        option enabled '1'
        option balance '1'
        option ref '0'

config policy 'special_policy'
        list use_iface 'WAN1'
        list use_iface 'WAN5'