Layer 2 vlans at separate sites

[Amendola24]

We have two layer 2 vlans with the same vlan ID but different subnets at two different locations. Site 1 vlan99 10.1.X.0, site 2 vlan99 10.1.Y.0. We want to move a server on 10.1.X subnet to be hosted in the location where 10.1.Y lives without having to re-ip the server so the clients on 10.1.X can still access it and not see any changes. How is this possible to accomplish if possible at all without making other larger changes to subnets/client PCs?

[Santikapo]

Do you have a network diagram showing routers and switches? 

Are you using any sort of tunneling between the sites?

[Amendola24]

IPSEC tunnels between the two sites. The route from layer 2 clients at site 10.1.X.0 would run from clients -> cisco access switch -> cisco core switch -> Foritgate -> over SDWan tunnel -> Fortigate at 10.1.Y.0 site -> cisco core switch -> cisco access switch -> server on 10.1.X.0.

[Santikapo]

VXLANs may be the solution you're looking for.

Here's a link to a an official Fortinet post regarding vxlans on FortiGate that might help you out:
https://community.fortinet.com/t5/FortiGate/Technical-Tip-VXLAN-over-IPsec-for-multiple-VLANs-using-...

You're most likely going to need additional dedicated interfaces on the each FortiGate in order to use Software Switches.

[ebilcari]

If this server/VM is going to be moved once (no frequent VM migration), I would suggest to reconfigure the IPs.