I'm pretty sure that you cannot advertise non Meraki VPN networks to Meraki VPN peers using the same MX. You need two and to use static routes. If you simply mean LANs on the MX, as long as their DG is the MX then they should find the non Meraki VPN subnets. ... View more

I'd plan for an outage.   If you change your subnet mask, you're going to have to update that on all devices with static IP configs.    Force devices on DHCP to refresh their IP address, and they should be updated. If you've got that outage window, you can also reboot your MX in order to clear its DHCP leases, if I recall correctly. I don't believe there's any other way to force an MX to clear its leases. ... View more