I went ahead a set up the Meraki MX like this, we use the MPLS connection as our primary connection, so I added a static route for 0.0.0.0/0 pointing to the MPLS router.   I don't believe this is a setup that is supported by Meraki.   We began having routing issues, PC's thinking they arent connected to the internet, etc.   Any experience with a setup like that? Is it supported?     ... View more

@MatthewHarrison as @PhilipDAth said, without NAT, the MPLS provider needs to know about all IP ranges on the site that you want to route over their network.  With NAT the MPLS provider only needs to know about the WAN interface of the MX.   A third option is to use auto VPN over the MPLS and set it to tunnel all traffic across, then the MPLS provider only needs to know about the MX WAN as the other subnets will be encapsulated within the encrypted VPN traffic stream. ... View more