Re: IPSEC S2S : From Meraki MX84 to Cisco Router is possible? If yes How?
Yes it is. You configure it in the Security & SD-WAN > Site-to-site VPN page.
If your MX is not already using AutoVPN you'll have to set it to hub mode for the Non-Meraki VPN settings to appear (UI limitation in my opinion). After that you can follow the instructions from this page: