Is it possible to have a default static route and a default route learnt by BGP active together?

[austinmas1987]

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[Yurisk]

Not a tested solution, but I'd think that if both ISPs links were part of an SD-WAN, which is implemented as Policy Based Routing in Fortigate, you could 'cheat' on ECMP limitation for routes learned via different protocols. You would need to create SD-WAN rules that would distribute traffic by volume to 2 lines equally.