I'm currently configuring an MX Firewall as a DHCP server and cant find an option to change the gateway IP address that DHCP allocates. This is required to support a migration as I want the MX to initially act as a DHCP server for the connected clients but for the clients to use the old firewall that is located on the same VLAN as their default gateway. Example below
Old Firewall (Gateway) - 192.168.1.1
New Meraki MX Firewall (DHCP Server) - 192.168.1.2
Clients - 192.168.1.10 - 200
Can I override the DHCP gateway using custom option 3?
Looking at the link that you attached, it appears that the Meraki MX will automatically respond with 'Option 3 - Router' using it local IP address, however its not really clear if you can override Option 3 and specify a custom IP address.
It looks like this is possible in the dashboard, but I'm not sure if the MX will honour this or if it will override and return its own IP address