Question : Dial-up server

Can anybody tell me how to install and configure something like dial-up server under linux.

Answer : Dial-up server

Everything depends on how you are handling a "dialup" server.

1) Hang modems off the linux box:

Easy way:
Get portslave
Get Cistron Radius
(both come with RH 6.x+)

Install portslave - it has some basic configuration settings to allow you to tell it how many ports to pay attention to, modem init strings, etc.

Install Cistron Radius - standard free radius server with lots of nice features.  You can add users to the users file (text file that contains user information, ip address info, etc), or to your /etc/password file for authentication.

Hard way:
Set up getty/mgetty to answer the modems w/ pppd - uses password file for authentication.  frankly, not worth the effort since portslave does it for you rather painlessly.

2)Have a RAS box (ie: PortMaster 3, USR Total Control, Ascend MAX, etc.)

Get Cistron radius.
Install it.
Read the readme for config (it's fairly simple, there are only about 3 or 4 files you need to edit and create a directory or two)
On the RAS unit tell it what the radius server ip address is, tell it what password it needs to use to gain access to radius, as well as the ip address of the logging server (simple way is use the same box for authentication as for logging).

Method 2 takes about 10 minutes to set up.

Method 1 takes about 15 or 20 minutes to set up.

Good luck!