Hey people, please settle down. Just one more nap till it's weekend ;-)
prtconf has been in AIX since 2001 I believe. It may have its origin in Solaris but I don't know that exactly.
Opus06, if you configure an interface just with ifconfig in AIX, you'll lose the config on reboot, because the it needs to be put in a database so that it can be re-applied on subsequent boots.
mktcpip will do that for you.
Furthermore, smit mktcpip or smitty mktcpip will build the mktcpip command line for you using an easy to use menu/dialog interface.
HTH,
p5wizard