Link Load balance 2 wan connections

You only need FGT, all that is needed is to create a Aggregate Interface (switch config needed as well), combining two or more physical interfaces.

Using an LACP trunk on 2 WAN interfaces will only increase your bandwidth if you are using one router, AND the link between FGT and router is saturated. I highly doubt this.

If you want to combine 2 ISP links to have their individual BW added up then you can either

• use one router capable of link bonding (viprinet.com for instance)

• use load balancing in FortiOS

But, both ways are different and have differing benefits.

Load balancing is done on the session level. Only complete sessions (transfers) will be using one of the 2 WAN links, alternatingly. With 1000s of sessions of comparable BW allocation this may well work for you.

Link bonding on the other hand will combine data streams on the bit level. This is far beyond the capabilities of a FGT. Link bonding routers can combine media of all sorts, like DSL, 3G/4G, cable/ethernet and so on. But they come at a price whereas FortiOS features are paid for as a whole.

That's absolutely correct, I've read the question in a hurry and pictured a different problem to solve :)

Now since we already told him that is was possible it would also be nice to show him how to accomplish the initial goal.

You can use this video as a guide to implement ECMP and dual wan links on 5.2 (you can also do it on 5.0 without the virtual-wan-link feature): http://cookbook.fortinet.com/redundant-internet-connections/ 

@drak:

I try not to rush things but to let the OP state what he/she really is intending. The solution follows that path then.