Multiple ISP with PalAlto

[Meed]

Hello,

I am setting up a new firewall stack with a new configuration that I have never tested and I have a few questions:

I have 3 ISPs that I want to configure as follows:

• 2 ISPs in active-active (so I'll have 2 routes 0.0.0.0/0 with equal cost)

• The third ISP will be used for a single use case, should I use the ECMP option with 3 Max Path (for the FIB table) and 3 NAT rules (one per ISP) or should I just use 2 Max Path of equal cost and configure the 3 ISP with a route to the exact destination and a NAT rule for this use case?

• What is the best Load Balance option for ECMP in my use case? A balanced Round Robin?

• I've created an aggregation group (LACP) with 3 sub-interfaces for the 3 ISPs, is this recommended or will it cause me problems? The 3 ISPs will be connected to a Cisco switch for redundancy.

• How does the DNS Proxy work in this case? Do I need to create a single DNS Proxy with the primary DNS of ISP1 and the secondary DNS of ISP2?

Thanks in advance