Dialup Server with Linux/*nix.

Posted on 2004-10-14
Last Modified: 2010-03-18
What would be some points/tips you might give me for going about setting up a dialup server to accept more than one connection at the same time?
Question by:firdanand
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Author Comment

ID: 12305838
Do I need a seporate phone line for each connection? Is there any way around this?

Expert Comment

ID: 12305852
Hi :-)

This is done with mgetty. You probably have it on your system, or can install it from your distribution CD.

Once you have it installed, to quickly get it running:

1. Modify /etc/mgetty+sendfax/login.config. Add this line there:
/AutoPPP/ -    a_ppp   /usr/sbin/pppd auth -chap +pap login kdebug 7

2. Modify /etc/inittab. Add this line there
mdm0:35:respawn:/usr/sbin/mgetty -D ttyS0
(Replace ttyS0 (and mdm0) to match your port number.
To make init "look" at the changes to  inittab, issue
kill -1 1

3. Dial your system with user credentials you create with useradd/passwd .
If this doesn't work (on some systems/mgetty versions it cannot work and you will have to create users on the ppp authentication file) replace the line you add to login.config to this:
/AutoPPP/ -    a_ppp   /usr/sbin/pppd auth -chap +pap name dialin kdebug 7
And add users by adding authentication lines to /etc/ppp/pap-secrets :
"myuser"        dialin   "password"      *
(replace myuser and password with the user and password respectively).


Author Comment

ID: 12312552
Yes, but how many connections would this be able to accept at the same time? I'll try not to get ahead of myself; I am essentially trying to set up something along the same lines as your average dialup ISP.
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Expert Comment

ID: 12331245
For every modem you will attach with 'mdm0:35:respawn:/usr/sbin/mgetty -D ttyS0', you will be able to connect one simultanious connection.

For example:
mdm0:35:respawn:/usr/sbin/mgetty -D ttyS0
mdm1:35:respawn:/usr/sbin/mgetty -D ttyS1
mdm2:35:respawn:/usr/sbin/mgetty -D ttyS2

The above is a 3 simultanious connections setup. There will be 3 phone numbers you can dial. You can ask your telecom company to create a "hunting" setup (users dial the first line, if busy the second modem rings and so on).

Expert Comment

ID: 12332070
But to supplement e-tsik. You will need a separate phone-line for every simultaneous user that connects to your system.

Could you illuminate a bit more on what you need to accomplish?

Author Comment

ID: 12336176
I am trying to create a LAN, over a very large area. Essentially, a WAN; a combination of ICS, LAN, and WAN, if you will.


1. Extreme cost efficiency.

2. Highest possible bandwidth between server and client.

3. High (but not priority) bandwidth connection to the internet.

4. 5-10+ simultaneous connections.

Our budget is on the small side, yet somewhat flexible. Ie. A phoneline for every single connection is out of the question.

Expert Comment

ID: 12346276
I suppose that the connections between the server and clients is not supposed to be a permanent one? Because with permanent connections you almost can't beat the vpn-solutions the telco's offer.

And one more time: you dont't need a phoneline for every single connection, you need a phoneline for every simultaneous connection! (you might consider this nitpicking, but I want to be sure that this is clear, since in your comment you are referring to "single connection")

But if 10+ phonelines are out of the question then your best bet is a decent internet access and tunnels to create a vpn. Depending on the bandwidth requirementss the clients might even get away with simple dial-up internet access. The server offcourse will need to have a permanent connection with a fixed ip-address.

Author Comment

ID: 12352972
Yes, I'm sorry, I meant, "simultaneous connection", every single simultaneous connection. They wouldn't be connected all the time, but I don't want to have a limit either.

So is that to say that your usual dialup ISP has hundreds of phone lines? Somehow I don't think that's so. Whenever I've used dialup, I always dial just one number, and I'm pretty certain that I'm not forwarded to another. Excuse me, but I really know very little about this. I have a somewhat good idea of what a VPN is, but isn't there a way to have someone use normal dialin, connect to the server, and then somehow connect to an IP address, freeing the phoneline.

By the way, thank you for all your help!

Accepted Solution

de2Zotjes earned 500 total points
ID: 12358133
an ISP will have hundreds of lines connected, really. Depending on where in the world you are the setups may differ a bit, but basically an ISP has a line and modem for every simultaneous connection. The fact that you feel that your connection is not forwarded just goes to show that modern digital telephone exchanges don't click and rattle anymore...

As for your last question: yes it is possible to use normal dialin, yes it is possible to connect to an ip-address  (using ppp for example) and yes it is possible to free the phone line, but after freeing the phone line your connection is gone! Freeing the phone line is dropping the connection. You can't have it both ways.

Author Comment

ID: 12358472
Thank you.

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