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21. dialin: Configuration of a Dial-In Server

21.1 dialin_config: How can I enable others to login via ISDN?

Some configuration examples can be found at: If you have trouble setting it up, try to obtain the latest packages for isdn4linux (see question distrib_getlatest). As usual, you can also ask in the mailing list. In general, there are several ways to configure dialin, depending on how you want others to dial in.

Here some more details for setting up the ttyI* devices. The setup is like for a serial port. Start a getty (mgetty from Gert Doering is highly recommended) on one of the ISDN devices (/dev/ttyI*). The entry in /etc/inittab looks like this:
I0:56:respawn:/usr/local/sbin/mgetty ttyI0
I1:56:respawn:/usr/local/sbin/mgetty ttyI1

The init string needs to be entered in the mgetty.config, since mgetty needs to know which MSN or EAZ to listen to. For example, if your MSN is 123456:
port ttyI0
modem-type data
speed 38400
init-chat "" ATZ OK AT&E123456 OK AT&B512 OK

For X.75 the block size was set to 512 bytes. Alternatively you can enter the entire configuration onto a single line in /etc/inittab (here printed on two lines!):
i0:45:respawn:/sbin/mgetty -D -m '"" ATZ OK AT&E123456 OK
AT&B512 OK' -s 38400 ttyI0

The most elegant way is to use iprofd. This daemon takes advantage of the AT&W0 command in the i4l modem emulation. You start iprofd with a path as parameter, e.g. "iprofd /etc/i4lprofile" Then with minicom or another terminal program, open an ISDN tty device and enter the necessary AT command by hand. When finished, enter the command AT&W0, then the kernel notifies iprofd to write the current configuration to the file. From now on it is enough to start iprofd in you isdn init script, and to initialize the appropriate ISDN tty devices with ATZ.

21.2 dialin_manyparallel: How can I allow several people to call in to me at the same time?

You have to configure exactly as many gettys or network interfaces as the number of people allowed to call in at one time. These gettys or network interfaces can be set to the same MSN, since several people can be connected to a MSN at the same time (as long as there are B channels free). However, not more than one getty can be assigned to a single ttyI* device.

21.3 dialin_manycards: When using several ISDN cards, how can I react upon on a call received via a specific ISDN card?

You can use the EAZ mapping feature for this to map incoming MSN numbers to new internal MSN numbers, in the same way as described for question dialout_manycards. Usage of a card can be prevented by using the dash during the mapping. Please note that it is not possible to have any limitations based upon the B channel, since channel assignment is normally done by the exchange.

21.4 dialin_analogditalsamettyi: Can I configure a ttyI* device to accept both digital and analog modem dialins?

Since the digital mode requires different register settings than the analog mode, this is not possible. Therefore you have to set up a two dedicated devices for this purpose. Please note that analog modem dialins are only possible if card and isdn4linux driver support it, which is only the case for a few cards.

21.5 dialin_fixedip: How can I assign fixed ip addresses per user who dials in via ipppd?

Just specify the fixed ip address with the user name and password in the pap/chap-secrets file (see man ipppd).

21.6 dialin_hdlc: Someone would like to dial in to my mgetty with HDLC. Is ttyI1 correct, or do I have to start with ttyI0?

No, it doesn't matter. It also has nothing to do with the number of the B channel (0 or 1). You just have to activate HDLC in the init string (ATS14=3).

21.7 dialin_autoppp: Is it possible with mgetty to automatically start pppd when LCP frames are received?

Yes, it is. This feature is called `AutoPPP'. See the configuration for mgetty.

21.8 dialin_passwd: How can I have (i)pppd check passwords from /etc/passwd instead of /etc/ppp/pap-secrets when someone dials in?

ipppd needs to be started with the options "login" and "auth". In /etc/ppp/pap-secrets, each user must have the following line to allow only certain users:

login-name * "" *

To allow all users simply:
* * "" *

The latter can also be achieved when the file pap-secrets does not exist.

21.9 dialin_ignored: I keep getting the message "isdn_tty: call from XXX - YYY ignored". Why does isdn4linux (syncPPP) ignore this dialin attempt?

There are two possible explanations. Either your own MSN (here: YYY) is not correctly set with "isdnctrl eaz interface YYY". Or "isdnctrl secure interface on" was set, without allowing calls from the incoming number (here: XXX) with "isdnctrl addphone interface in XXX".

21.10 dialin_async: A SunISDN tries to dial into my i4l system.

The Sun tries to communicate with asyncPPP. ipppd can't handle this, you have to use the ttyI* devices and the standard pppd.

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