Yes, we use a similar design but we use dumb layer 2 switches for the WAN side of the MXs i.e. Provider 1 -> L2 switch 1 -> WAN 1 on both MX84s. Provider 2 -> L2 switch 2 -> WAN 2 on both MX84s We have 3x IPs from each WAN provider as the HA uses the WAN, not the LAN side in SDWAN mode so that you ensure traffic continuity during failover of MX. One goes to each MX and one is the floating 'virtual' address. On the LAN side we have 1 port from each MX into two different L3 switches that are stacked together (Cisco 3850s in our case). We use a dedicated VLAN and subnet for the MX to 3850 connection but you could trunk if you prefer.
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