How to run multiple sites on the same port?

Question

IIS

Good afternoon.
I have 2 sites on asp.net core, they work fine separately.
I do "add an application" to the first side, I set up both sites work and open, but then the problem is the following: the first site has the address " localhost:81 ", the second " localhost:81/site2 "
When you try to do something on the second site, an additional postscript" site2" disappears and the site is down, the first site is functioning normally.
Application pools are different, everything is running on Windows Server 2012 R2.
Please tell me how to fix.