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6. Configuring a RAW AX.25 connected mode interface.

The first stage to configuration of an AX.25 interface is to configure it to work as a `vanilla' AX.25 interface with no TCP/IP. The following configuration will get you to the point of being able to make AX.25 calls from your Linux machine to other AX.25 nodes.

The AX.25 software has been designed to work with a TNC in kiss mode or with other cards such as the Ottawa PI2 card, PacketTwin and other SCC cards via special drivers that emulate a kiss tnc.

For real KISS TNC's there are two steps to complete in order to create an AX.25 port ready to use to make outgoing calls. For other types of hardware you need only complete the first step.

6.1 Creating the /usr/local/etc/axports file.

The AX.25 ports have a configuration file that is read by many programs that want to find information about an AX.25 port. This file is called the:

/usr/local/etc/axports

file. The format of the file is as follows:

portname  callsign  baudrate  paclen  window  description

where:

portname

is a text name that you will refer to the port by.

callsign

is the AX.25 callsign you want to assign to the port.

baudrate

is the speed at which you wish the port to communicate with your TNC.

paclen

is the maximum packet length you want to configure the port to use for AX.25 connected mode connections.

window

is the AX.25 window (K) parameter. This is the same as the MAXFRAME setting of many tnc's.

description

is a textual description of the port.

In my case, mine looks like:

radio    VK2KTJ-0        4800    256     2       144.800 MHz

6.2 Creating the AX.25 device

If you are using an SCC card like the PI2 or PacketTwin then you do not need to create the network device, as the kernel driver will automatically do this for you. If you are using a KISS TNC then you will need to create the AX.25 interface as it will not already exist. Creating an AX.25 port is very similar to creating a slip device.

You will need to have the TNC preconfigured and connected to your serial port. You can use a communications program like minicom or seyon to configure the TNC into kiss mode if you wish.

You use the axattach program in much the same way as you would use the slattach program (refer to the NET-2-HOWTO for more information on slattach and the other network software for Linux). For example:

# /usr/local/sbin/axattach /dev/ttyS0 radio

would configure your /dev/ttyS1 serial device to be a kiss interface configured as per the details for the line beginning with the portname "radio" in the /usr/local/etc/axports file.

All this step has done is to actually activate the device in the kernel, you need to run other programs before you an actually make use of the port.

Setting the callsign for SCC cards.

If you are using a PI or PacketTwin card then you should use the axparms -setcall command to change the callsign of the appropriate port to that which you intend to use. Refer to the PI/PacketTwin section for the names of the network devices to use.

Testing the interface.

You now should be able to make outgoing AX.25 connections. To test AX.25 connected mode you could use the call program as demonstrated:

/usr/local/bin/call radio VK2DAY via VK2SUT

Note: you must tell call which AX.25 port you wish to make the call on, as the same AX.25 node might be reachable on any of the ports you have configured.

The call program is a linemode terminal program for making AX.25 calls. It recognises lines that start with `~' as command lines. The `~.' command will close the connection.

Please refer to the man pages in /usr/local/man and the README file in ax25-utils-2.0.0 distribution for more information.


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