How to use SSH on local network

Introduction

This comprehensive tutorial explores SSH (Secure Shell) configuration and usage within a local network environment, focusing on Linux systems. Designed for system administrators and developers, the guide provides practical insights into establishing secure, efficient remote connections using SSH protocols and best practices.

SSH Fundamentals

What is SSH?

SSH (Secure Shell) is a cryptographic network protocol that enables secure remote access and communication between computers over an unsecured network. It provides a secure channel for executing commands, transferring files, and managing network devices.

Key Features of SSH

SSH offers several critical security features:

Feature	Description
Encryption	Protects data transmission using strong encryption algorithms
Authentication	Verifies user identity through passwords or cryptographic keys
Integrity	Ensures data hasn't been tampered with during transmission

SSH Connection Workflow

SSH Authentication Methods

Password Authentication
- Simple but less secure
- Vulnerable to brute-force attacks
Public Key Authentication
- More secure method
- Uses cryptographic key pairs

Basic SSH Command Structure

ssh username@hostname

Key Components of SSH

SSH Client: Software used to connect to remote systems
SSH Server: Daemon listening for incoming connections
SSH Keys: Cryptographic keys for secure authentication

Use Cases for SSH

Remote server administration
Secure file transfers
Tunneling network traffic
Automated script execution

SSH Security Best Practices

Use key-based authentication
Disable root login
Configure firewall rules
Regularly update SSH software

At LabEx, we recommend mastering SSH as a fundamental skill for Linux system administrators and network professionals.

Local Network Configuration

Network Prerequisites

Identifying Local Network Devices

## List network interfaces
ip addr show

## Discover network devices
sudo nmap -sn 192.168.1.0/24

SSH Server Installation

Installing OpenSSH Server

## Update package list
sudo apt update

## Install SSH server
sudo apt install openssh-server

## Verify SSH service status
sudo systemctl status ssh

Network Configuration Steps

1. Configure SSH Server

## Edit SSH configuration file
sudo nano /etc/ssh/sshd_config

SSH Configuration Parameters

Parameter	Recommended Setting	Purpose
Port	22 or custom port	Network access point
PermitRootLogin	no	Enhance security
PasswordAuthentication	no	Enforce key-based auth

2. Firewall Configuration

## Allow SSH through UFW
sudo ufw allow ssh

## Enable firewall
sudo ufw enable

Local Network SSH Connection Workflow

IP Address Configuration

Static vs Dynamic IP

## Check current IP configuration
ip addr show

## Configure static IP (example)
sudo nano /etc/netplan/01-netcfg.yaml

SSH Key Generation

## Generate SSH key pair
ssh-keygen -t rsa -b 4096

## Copy public key to remote machine
ssh-copy-id username@remote_host

Troubleshooting Network Issues

Common SSH Connection Problems

Firewall blocking port
Incorrect network configuration
SSH service not running

Security Considerations

Use non-standard SSH ports
Implement fail2ban
Regular system updates

At LabEx, we emphasize the importance of secure and efficient local network SSH configurations for seamless remote access and management.

Secure SSH Practices

Authentication Hardening

Key-Based Authentication

## Generate SSH key pair
ssh-keygen -t ed25519 -f ~/.ssh/labex_key

## Copy public key to remote server
ssh-copy-id -i ~/.ssh/labex_key.pub username@remote_host

Disable Password Authentication

## Edit SSH configuration
sudo nano /etc/ssh/sshd_config

## Set these parameters
PasswordAuthentication no
PermitRootLogin no

Advanced Security Configurations

SSH Configuration Best Practices

Security Parameter	Recommended Setting	Purpose
Protocol	2	Use latest SSH protocol
MaxAuthTries	3	Limit login attempts
AllowUsers	specific_userlist	Restrict user access

Firewall and Intrusion Prevention

UFW Configuration

## Configure firewall
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow from 192.168.1.0/24 to any port 22
sudo ufw enable

Fail2Ban Implementation

## Install fail2ban
sudo apt install fail2ban

## Configure jail for SSH
sudo nano /etc/fail2ban/jail.local

SSH Connection Workflow Security

Advanced Encryption Techniques

Cipher and MAC Configurations

## Recommended SSH ciphers
Ciphers [email protected],[email protected]
MACs [email protected]

Monitoring and Logging

SSH Access Tracking

## View SSH login attempts
sudo tail -f /var/log/auth.log

## Monitor current connections
who

Additional Security Tools

SSH Port Knocking
Two-Factor Authentication
VPN Integration

Regular Maintenance

Update and Patch

## Regular system updates
sudo apt update
sudo apt upgrade
sudo systemctl restart ssh

Security Audit Tools

Recommended Scanning Tools

OpenVAS
Lynis
ClamAV

At LabEx, we emphasize continuous learning and implementation of robust SSH security practices to protect your network infrastructure.

Summary

By mastering SSH techniques on local networks, Linux users can enhance system connectivity, improve remote management capabilities, and implement robust security measures. The tutorial equips professionals with essential knowledge for creating reliable and secure network communications across Linux-based infrastructure.