Yes you need 2 or 3 ip's from each isp. "Ensure that both MXs have their own uplink IP address for dashboard connectivity as described in the Uplink IP Configuration section. If a virtual IP is being used, an additional IP address is needed, and all three IPs must be in the same subnet." https://documentation.meraki.com/SASE_and_SD-WAN/MX/Design_and_Configure/Deployment_Guides/MX_Warm_Spare_-_High_Availability_Pair#Requirements_and_Best_Practices
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