The VPN tunnel is established. The Cisco Meraki cloud already knows VLAN and subnet
information for each MX, and now, the IP addresses to use for tunnel creation. The dashboard
and MXs establish two 16-character pre-shared keys (one per direction) and create a 128-
bit AES-CBC tunnel. Meraki Auto VPN leverages elements of modern IPSec (IKEv2, DiffeHellman and SHA256) to ensure tunnel confidentiality and integrity. Local subnets specified
in the dashboard by admins are exported across the VPN
meraki_whitepaper_autovpn.pdf (cisco.com)
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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