warm spare is not active active. you could run both providers to both mx's if you have enough IP addresses between the provider and your MX's . https://community.meraki.com/t5/Security-SD-WAN/Does-MX-device-can-support-dual-active/m-p/64242#M16273 so the WAN ports can be both active, but not Both MX's (in warm spare) at the same time
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