slattach Command in Linux

---

---

The slattach command is used to attach a network interface to a serial line, allowing you to use it for point-to-point links to other computers. This can be particularly useful when working with serial connections, such as connecting to a router or another computer via a serial port.

The slattach command is a small utility that can put a normal terminal (serial) line into one of several network modes. This allows you to use the serial line for network communication. The command supports various protocols, including SLIP (Serial Line Internet Protocol), CSLIP (Compressed SLIP), PPP (Point-to-Point Protocol), and KISS (used for AX.25 packet radio terminal node controllers).

Table of Contents

Here is a comprehensive guide to the options available with the slattach command −

• Understanding the slattach Command
• Syntax of slattach Command
• slattach Command Options
• How to Use slattach Command in Linux?
• Examples of slattach Command in Linux
• Attaching a Network Interface
• Use Cases of slattach Command in Linux
• Practical Considerations

Understanding the slattach Command

The slattach command in Linux serves a specific, though now somewhat archaic, purpose: it's used to attach serial lines as network interfaces, primarily for Serial Line Internet Protocol (SLIP) connections. Essentially, it bridges the gap between a serial port and the network stack, allowing data to be transmitted over a serial link as if it were a network connection.

This was particularly relevant in the past for dial-up connections or direct serial connections between machines. While SLIP has largely been superseded by PPP (Point-to-Point Protocol), understanding slattach provides insight into the historical evolution of networking in Linux and the underlying mechanisms of serial communication. Key aspects include its reliance on TTY devices, the ability to set baud rates, and its role in configuring network interfaces through commands like ifconfig.

Syntax of slattach Command

The basic syntax for the slattach command is −

slattach [options] <tty_device> [baudrate]

Here, in this syntax −

• tty_device − The terminal device associated with the serial port (e.g., /dev/ttyS0).
• baudrate − The baud rate for the serial connection (e.g., 9600, 115200).

slattach Command Options

Some common options for slattach include −

How to Use slattach Command in Linux?

Despite its diminished relevance in modern networking, slattach highlights the adaptability of the Linux kernel and its ability to handle diverse communication protocols. Its function exemplifies the core principle of treating devices as files within the Linux environment, where serial ports are represented as TTY devices.

Furthermore, examining slattach's operation can be a valuable exercise in understanding low-level network configuration and the historical context of network protocols. While not commonly used today, its existence underscores the evolution of network technologies and the underlying principles that continue to inform modern network design.

Examples of slattach Command in Linux

Let's explore various examples of using the slattach command −

• Basic Usage
• Using CSLIP Protocol
• Running in the Background
• Using a Different Baud Rate
• Checking the Network Interface
• Detaching the Interface

Basic Usage

Attach a network interface to a serial line using /dev/ttyS0 at a baud rate of 115200.

sudo slattach -s 115200 /dev/ttyS0

This command attaches the serial line to /dev/ttyS0 with a baud rate of 115200. The default protocol used is SLIP (Serial Line Internet Protocol).

Using CSLIP Protocol

Attach a network interface using CSLIP (Compressed SLIP) protocol.

sudo slattach -p cslip -s 115200 /dev/ttyS0

In this example, the -p cslip option specifies that the CSLIP protocol should be used.

Running in the Background

Run slattach in the background.

sudo slattach -d -s 115200 /dev/ttyS0

The -d option detaches the command from the terminal and runs it in the background.

Using a Different Baud Rate

Use a baud rate of 9600.

sudo slattach -s 9600 /dev/ttyS0

This command sets up the connection with a baud rate of 9600.

Checking the Network Interface

After attaching a serial line, you might want to check the network interface.

ifconfig sl0

sl0 is the default network interface created by slattach when using the SLIP protocol.

Detaching the Interface

Detach the network interface from the serial line.

sudo ifconfig sl0 down
sudo slattach -d /dev/ttyS0

The first command brings down the sl0 interface, and the second command detaches slattach from /dev/ttyS0.

Attaching a Network Interface

When you use slattach, it creates a new network interface (e.g., sl0) that you can use to send and receive network packets over a serial connection. This is useful for networking equipment that does not have a standard Ethernet connection.

Protocols

• SLIP (Serial Line Internet Protocol) − The most basic protocol that allows IP packets to be sent over a serial line.
• CSLIP (Compressed SLIP) − A variation of SLIP that includes header compression to reduce the overhead of IP packets.
• PPP (Point-to-Point Protocol) − A more advanced protocol that supports authentication, encryption, and compression.
• KISS (Keep It Simple Stupid) − A protocol used for communicating with AX.25 packet radio terminal node controllers.
• Adaptive − Allows slattach to automatically adapt to different protocol types.

Use Cases of slattach Command in Linux

• Remote Access − Connect to remote devices, such as routers or other computers, over a serial line.
• Embedded Systems − Communicate with embedded systems that use serial ports for networking.
• Network Testing − Set up a test network using serial connections for development or troubleshooting.

Practical Considerations

• Baud Rate − Ensure that the baud rate matches on both ends of the serial connection.
• Permissions − You may need root privileges to use slattach and configure network interfaces.
• Monitoring − Use tools like ifconfig or ip to monitor the status of the network interface.

Conclusion

The slattach command is a versatile tool for attaching network interfaces to serial lines in Linux. It supports various protocols and can be run in the background for long-term connections. By understanding the different options and use cases, you can effectively use slattach for serial network communications. This allows for a uniform interface to manage various hardware components.