External IP's

hi,

and welcome to the forums.

There is a solution which would connect your server to the router via a "transparent VDOM" but...this setup is not simple. As I'm not sure what your requirements are, let me ask: why not NAT? Can't the server use a private address, or one of your public addresses (say, 1.2.3.4), while you NAT it to another public address (say, 1.2.3.5)?

I think one way you could do this is by connecting the server to another router and the router to a spare port on the Fortigate.

The port on the Fortigate needs to have a random /31 IP on it, the router the other IP from /31 range.  The server can be connected to this router and use a /31 again for the router and server connection.  The public IP on the router will over lap with the IP in the rest of your network, but as long as the server never needs to reach that 'real' IP it won't matter.  The Fortigate needs to be configured with a static route pointing x.x.x.server/32 to the the random /31 IP used for the router and the router needs a default route back to the random /31 on the Fortigates' interface.

You can then configure policies needed between External port and the new port where the server is.

Does that make sense at all?  I can't say I have tried this, but logically I think it should work...