Red Hat ISDN config

3. Extended Configuration

3.1 Network

If your ISP doesn't use the normal network addresses (last byte of the IP is 0) and broadcast addresses (last byte is 255), you must enter the correct values here. You should get these information from your ISP.

3.2 Netmask

See 3.1 Network

3.3 Callback

With the callback mode "in" your computer connects to the indicated ISP as soon as it gets a calling of the telephone number "dialin telephone number". Some companies use this type of callback, in order to prevent the abuse of the access at the firm expense, since in this case always the account of the customer is loaded with the fees.

The callback mode "out" operates the other way around. Your computer calls the receiving station, then waits however not for an acceptance of the call, but hangs up immediately and waits for the recall. This mode is used e.g. with some teleworkstations, with which the company takes over the on-line costs of its tele workers.

Callback mode "off" deactivates the callback system.

3.4 Telefonnumber of caller

Unless 'Permitted Telefonnumbers' is deactivated, only these calling numbers may trigger a callback.

3.5 Timeout for callback

Time in seconds until a callback is initiated.

3.6 Permitted Telefonnumbers

If this checkbutton is activated, only configured callers may connect. Please make sure that this button is enabled if you use rawip, unless you want to allow everybody to connect to your computer without auhentification.

3.7 Idle timeout

If an online connection isn't used for a while, ISDN4Linux can terminate the connection automatically. With the menu option "Inactivity timeout" you can change the default value of 240 seconds. For interactive connections such as telnet or ssh you should select a somewhat longer timeout, since with dynamic IPs after terminating the ISDN connection these programs can't continue to work, because your computer will possibly get another IP.

3.8 Debug Messages

Sometimes it may occur that despite all attempts the creation of a functional ISP configuration doesn't succeed. In this case activate the debugging and restart the ISDN system. When you retry to connect to the ISP there will appear more detailed messages in the file /var/log/messages, which are sometimes very helpful to detect the error. Please deactivate the debug mode when the configuration is finished, otherwise the log file will grow very fast.

3.8 Packet sizes (MTU/MRU)

Sometimes the syncppp protocol can't come to terms about the size of the TCP/IP packages. In this case you'll have to set the size here.

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