Auto VPN Configuration Details
Enable Auto VPN by defining how the WAN Appliance will communicate with the rest of the Auto VPN domain
If the WAN Appliance is configured as a Hub, it will build VPN tunnels to all other Hub WAN Appliances in the Auto VPN domain (in the same dashboard organization). It will also build VPN tunnels to all Spoke WAN Appliances in the Auto VPN domain that have this WAN Appliance configured as a hub. If all WAN Appliances in the Auto VPN domain are configured as Hub then the Auto VPN has a full mesh topology.
If the WAN Appliance is configured as a Spoke, it will build tunnels to only the WAN Appliances that are configured as its Hubs. If the majority of WAN Appliances in the Auto VPN domain are configured as Spoke with only a few key locations (such as data centers or headquarters) configured as hubs, then the Auto VPN environment has a hub-and-spoke topology.
Full Tunnel or Split Tunnel
By default all WAN Appliances in the Auto VPN domain (dashboard organization) will only send traffic to an Auto VPN peer if the traffic is destined for a subnet contained within the Auto VPN domain. This is often referred to as 'split-tunnelling,' meaning that VPN-subnet-bound traffic is sent over VPN, and other traffic is routed normally via the primary WAN Appliance WAN uplink. If an organization wants to route all traffic (including traffic not contained within the Auto VPN domain) through a specific hub site, this is referred to as 'full-tunneling.'
Note that full-tunneling only affects client data and all Meraki management traffic will egress directly via the primary WAN regardless.
To configure full-tunneling in a full mesh topology simply define an Exit hub from the WAN Appliances in the Auto VPN domain.
https://documentation.meraki.com/MX/Site-to-site_VPN/Meraki_Auto_VPN_-_Configuration_and_Troubleshoo...
For the question 3 the answer is yes.
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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