2 Public address routing to different ports of Application Server

You don't need either in the situation you have described.

You'll create 2 pools, pl_server_p1 and pl_server_p2, and 2 virtual servers, each with a public IP, and each pointing to a particular pool.

Then I guess I would use route domain only when I want to isolate connections between Testing and Production environment ?

Route domains have 2 main use cases;-

• overlapping address space
• separation of security zones in such a way as to prevent 'accidental' crossing of the streams (like someone configuring a forwarding virtual with a destination of "cust a" enabled on a "cust b" self IP).

It's up to you whether separation of test and production traffic warrants a route domain, in fact there may be cases where it would be useful to point a test VIP at a prod server and a route domain may inhibit this.

Thank you so much, it's really helpful :)