Windows Server:

The Default model is in C:\<installation path>\wa\bin

- The following file define the default interface in parameter internetAccessMethod
default.htm

- The following file define the cgi interface in parameter internetAccessMethod
default-cgi.htm

- The following file define the isapi interface in parameter internetAccessMethod
default-isapi.htm

Sample: var internetAccessMethod = 'bmc-ctd-wa-cgi.exe';

To set default to isapi:
- replace the content of file default.htm with the content of file default-isapi.htm
- save the default.htm 

To set default to cgi: 
- replace the content of file default.htm with the content of file default-cgi.htm
- save the default.htm


NOTES:

- To take the new default.htm file, the end users must clear their web browser cache to get rid of the old default.htm file.

- A cgi is a program started by the Web Server, per requests from browser.
It opens a new process to run its code and this can fail with timeout.

- ISAPI is a dll in memory.
There is no new process created, but just a thread using this dll.
This dll will never timeout!

There is no good or bad method, it depends on your local policy.
cgi if you prefer too long request to fail with timeout.
ISAPI if you trust your end user will not go beyond a reasonable limit.
 

Linux Server using APACHE:

Check the http.conf file