F.6.2.3. Working With the CTC Device Driver

A Channel-to-Channel (CTC) connection is the typical high speed connection between mainframes. The CTC device driver can be used to establish a point-to-point TCP/IP or tty connection between two Linux for zSeries and S/390 instances or between a Linux for zSeries and S/390 instance and another mainframe operating system instance such as z/OS, OS/390, z/VM, or z/VSE.

The CTC driver assigns a base interface name like the following:

ctc<n>

The value <n> is an integer that uniquely identifies the device. <n> is 0 for the first device of that type, 1 for the second, and so on.

Load the device driver:
```
# modprobe ctc
```
Create the group device:
```
# echo <read_device_bus_id>,<write_device_bus_id> > /sys/bus/ccwgroup/drivers/ctc/group
```
Due to the length of this command, it has been broken into two lines.
Configure the device.

Set the protocol:
```
# echo <protocol> /sys/bus/ccwgroup/drivers/ctc/<device_bus_id>/protocol
```
Where <protocol> is 0, 1, 2, or 3.

0 — This protocol provides compatibility with peers other than OS/390, or z/OS, for example, a VM TCP service machine. This is the default.

1 — This protocol provides enhanced package checking for Linux peers.

2 — This protocol provides a CTC-based tty connection with a Linux peer.

3 — This protocol provides compatibility with OS/390 or z/OS peers.

For more information about configuration of the CTC driver, refer to the following:

http://oss.software.ibm.com/developerworks/opensource/linux390/docu/lx26apr04dd01.pdf (Linux for zSeries and S/390 Device Drivers, Features, and Commands)

Set the device online:

# cho 1 /sys/bus/ccwgroup/drivers/lcs/<read_device_bus_id>/online

Define the alias.

Based on the type interface being added, add a line to /etc/modprobe.conf that is like the following:
```
ctc<n> alias ctc
```

Create a configuration script.

Create a file in /etc/sysconfig/network-scripts/ with a name like the following:

ifcfg-ctc<n>

The file should look like the following:

/etc/sysconfig/network-scripts/ifcfg-ctc0
# IBM CTC
DEVICE=ctc0
BOOTPROTO=static
IPADDR=192.168.70.136
GATEWAY=172.16.70.136
NETMASK=255.255.255.255
ONBOOT=yes
SUBCHANNELS=0.0.1b00,0.0.1b01
NETTYPE=ctc
CTCPROT=0
TYPE=CTC

Activate the device.

Based on the type interface being added, issue an ifup command:
```
# ifup ctc<n>
```