multiple WAN interfaces and failover rules when 3 or more WAN interfaces

Question

Say we have 3 WAN interfaces WAN1, WAN2 & WAN3 - WAN1 is the first choice and WAN3 last preferred WAN interface. (1) Is it possible to specify more than one backup - and if so can I specify the order of activation 
 (2) if not, how best configure the WAN interfaces to best match our order of choice 
 (3) same question again if I add an extra WAN interface (say WAN4) 
 Could you please indicate the relevant KB, manual, ... 
 Thanks JL

LuCar Toni · Answer

Hi, 
 Most of my customers uses the primary gateway in a rule for a specific interface and the backup interface, they use "WAN Loadbalancing". So basically most of the time, if WAN1 fails, the traffic will be load balancing over WAN2/WAN3 - depending on the Load balancing settings. 
 WAN1 is the "strongest" connections. And with MR3, you can failback to the WAN1 connection, if this fails. 
 Additionally to say, if WAN2 in this scenario fails, WAN3 will take place of course. So you can configure WAN2 as 95% and WAN3 as 5% to have the (worst) case covered, WAN1 and WAN2 fails at the same time. 
 Here are some rules about this: https://community.sophos.com/kb/en-us/123530