@TimBisel wrote:
Ok, you are right so far, but two things.
1.What am I missing on why the MX is still reachable?
I believe this is because the connections to the MX are handled by the "input" firewall rules and the traffic to devices in the other VLAN are handled by the "forward" firewall rules. Many firewall devices have two separate sets of rules, one for traffic destined for the device (input) and one destined for devices on the other side (forward). Because the pings that are destined for the MX itself, the packets never go through the "forward" rules, even if they are for a different interface than the one they come in on.
In the case of the Meraki, the "input" rules seem to be governed by the "Security appliance services" rules for the outside interface and things like the "Local device status page" for the inside interfaces.