Yes, the redundancy between the MXs is via Warm Spare.   If you are talking about SD-WAN specifically, you can create SD-WAN Policies to forward traffic to a specific WAN link.   https://documentation.meraki.com/MX/Firewall_and_Traffic_Shaping/SD-WAN_and_Traffic_Shaping#Flow_preferences ... View more

OSPF on the MX only redistributes specific SD-WAN routes into the OSPF protocol for use in your campus network. ... View more