IP Sec TUnnel - Same Internal Subnet in Both Sides

[diablo3077]

Good Morning Everyone,

I would like to ask for your help with the issue I need to resolve.

I'm using subnet 10.0.0.0/24 to connect some local agents to one of our clients remote subnets through an IP Sec Tunnel and everything's OK so far.   Now, those local agents must join a domain and when that happens IP Addresses will change to 10.16.0.0/24 subnet, but my client told me he has the same subnet on their side, so he can't add it to the Encryption Domain in the IP Sec Tunnel.  As I have the rest of my company in the 10.16.0.0/24 subnet is not possible to change it, the remote SysAdmin told me to setup my firewall (Fortigate 200E) to change my local IP addresses automatically to any 10.218.0.0/24 subnet IP Address, which he will add to the Encryption Domain, but unfortunately that procedure isn't clear for me due that is the first time something like that happens to me, so I appreciate your help giving me your recommendations or links to get some information.    Thank you very much! CARLOS D.

[techevo]

Take a look at this : https://docs.fortinet.com...th-overlapping-subnets