The SD-Wan runs in a "out-of-band management" interface. That is a pre-configured VLAN that will try to get a DHCP address. This is configured on the "Switch Settings" sections of the "Switch" tab of the Meraki Dashboard.  If this interface doesn't get Internet connection, it will try to go via any of the trunked VLANs configured in the switch. The switch will try any method to reach the Meraki DCs. Therefore, you need to make sure that this Management VLAN has internet access, but the rest is all layer 2. ... View more