VLAN overlaps Z4 to forti VPN establishing

[Abdul salaam]

Hi engineers, 

Trying to build site to site vpn from Z4 Meraki to forti firewall but meraki dashboard pop below messages, What would be the reason and the solution ? 

The VLAN subnet 172.21.16.8/29 overlaps with a remote VPN subnet on the non-meraki peer Forti-W1 (172.16.0.0/12). IP traffic will be routed to the smallest subnet that Contains the IP address.

The subnet on the non-meraki peer Forti-W1 (172.16.0.0/12) overlaps with the subnets on networks London1 (172.21.16.0/29) and Z4 (172.21.16.16/29). IP traffic will be routed to the smallest subnet that Contains the IP address.

[M02@rt37]

Hello @Abdul salaam,

If you can not Re IP with new subnet, consider to use NAT through NAT Policy. NAT the IP packet source, NAT the IP packet destination also. Inform remote admin for doing NAT also on their side.