Quoting israel.garcia@cimex.com.cu:

Hi, I have a serial modem connected to /dev/ttyS0 on my CentOS server, I want to set up this server to allow connections through this serial modem but only to the console.... (I want to log in)...

PS: I don't want PPP, I just want to get my linux console through this serial modem...

What do I have to configure on my linux?

Hmmm... Do you want *console* (as in /dev/console) or just terminal access (as in /dev/ttySO)?