The Non-Meraki VPN tunnel will only be established between the Active WAN interface and the configured non-Meraki VPN peer. Typically, the WAN1 interface is the Primary interface, and assuming it is up, it will be considered the active interface, and the Non-Meraki VPN tunnel will be established over WAN 1 only (Port 3) and not WAN2 (Port 4). The MX will try to establish the VPN tunnel to the Non-Meraki Peer if WAN1 fails or if WAN2 is the Primary connection. You can change which WAN interface is the Primary interface on the "Security & SD-WAN > Configure > SD-WAN & Traffic Shaping" Page.
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