Hello Paolo,
Are all the SMP, HCL and CLT systems non-SAP systems? I see that you are using the EXTSRV argument. This is to be used when the backend is not an SAP ABAP/Java/dual-stack system.
In addition, you have "wdisp/system_3" defined twice.
And what is "app2", "app1" and "app2.com"? Are these virtual hostnames / DNS aliases that point to the Web Dispatcher server?
Regards,
Isaías