Hi hosokawaw, Generally its not recommended that the "heartbeat" cable between a warm spare pair of MX devices be a direct link. Recommendations can be found in the link below, a switch which has connections to both MX LAN segments is preferred. https://documentation.meraki.com/MX/Deployment_Guides/MX_Warm_Spare_-_High_Availability_Pair#Recommended_Topologies
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