Flow Preferences By default (without load balancing), internet-bound traffic will flow out of the MX's primary uplink. The MX can also be configured to send traffic out of a specific interface based on the traffic type (policy-based routing), or based on the link quality of each uplink (performance-based routing). Flow preferences can be configured to define which uplink a given flow should use. Flow preferences will also supersede load balancing decisions.  Internet Traffic Flow preferences for internet-bound traffic can be configured to force traffic over a specific uplink based on its source and/or destination. These preferences can be used if a specific uplink should be designated for a particular type of traffic, such as traffic bound for a cloud-hosted service.  Note: ICMP traffic is not subject to traffic shaping rules. As a result, Flow Preference will have no impact on ICMP traffic. To create a flow preference for internet traffic: In Dashboard, navigate to Security & SD-WAN > Configure > SD-WAN & Traffic shaping. Navigate to Flow preferences, and under Internet traffic, select Add a preference. Define the traffic that will be assigned a designated uplink: Protocol - TCP, UDP, or Any. Source - Source IP, using CIDR notation. Src port - Source port, or "Any". Destination - Destination IP, using CIDR notation. Dst port - Destination port, or "Any". Preferred uplink - The uplink this traffic will be sent over. Click Save Changes.           ... View more

I remember having to call Meraki support and asking them to enable that.  ... View more