How to SSH Via Jump Server or Bastion Host: A Comprehensive Guide

In today’s fast-paced world, secure remote access has become increasingly critical. Whether working from home, on a business trip or managing a distributed team, you need access to your servers from anywhere, anytime. However, granting direct server access is risky and can lead to security breaches. Organizations use jump servers or bastion hosts to provide secure server access. This article will explain what jump servers and bastion hosts are and how to SSH via jump server or bastion host.

Understanding Jump Servers and Bastion Hosts

Jump servers and bastion hosts are network security devices used to provide secure remote access to servers. They act as a gateway between the remote user and the server. When a user needs to access a server, they first connect to the jump server or bastion host, and then the jump server or bastion host connects to the target server.

Jump Servers

A jump server is a server placed in a demilitarized zone (DMZ) that acts as a bridge between the remote user and the target server. Jump servers are used to access servers in private networks that are not directly accessible from the internet.

Bastion Hosts

A bastion host, also known as a jump host, is a special-purpose computer that is designed to be the sole point of entry for remote administrators. The bastion host is placed in a DMZ, and all traffic passes through it. The bastion host is hardened to withstand attacks and is audited regularly.

SSH via Jump Server or Bastion Host

Now that you understand what jump servers and bastion hosts are, let’s dive into how to SSH via jump server or bastion host.

Prerequisites

Before you begin, you need to have the following:

• Access to a jump server or bastion host
• Access to the target server
• SSH client installed on your local computer

SSH via Jump Server

To SSH via jump server, follow these steps:

1. Open a terminal on your local computer.

2. Type the following command to connect to the jump server:

ssh username@jump_server_ip_address

Replace username with your username and jump_server_ip_address with the IP address of the jump server.

3. Once you are connected to the jump server, type the following command to connect to the target server:

ssh username@target_server_ip_address

Replace username with your username and target_server_ip_address with the IP address of the target server.

4. Enter your password when prompted.

5. The jump server connects you to the target server.

SSH via Bastion Host

To SSH via bastion host, follow these steps:

1. Open a terminal on your local computer.

2. Type the following command to connect to the bastion host:

ssh -A username@bastion_host_ip_address

Replace username with your username and bastion_host_ip_address with the IP address of the bastion host. The -A option enables agent forwarding, which allows you to use your local SSH key to authenticate with the target server.

3. Once you are connected to the bastion host, type the following command to connect to the target server:

ssh username@target_server_ip_address

Replace username with your username and target_server_ip_address with the IP address of the target server.

4. Enter your password when prompted.

5. You are now connected to the target server via the bastion host.

Using SSH Config File

SSH configuration file, ssh_config, can be used to simplify the SSH connection process. The SSH configuration file can be found in the ~/.ssh directory on your local computer.

To SSH via jump server or bastion host using the SSH configuration file, follow these steps:

1. Open the SSH configuration file in a text editor:

nano ~/.ssh/config

2. Add the following lines to the file:

Host jump_server_alias
    Hostname jump_server_ip_address
    User username

Host target_server_alias
    Hostname target_server_ip_address
    User username
    ProxyJump jump_server_alias

Replace jump_server_alias and target_server_alias with aliases that you choose. Replace jump_server_ip_address with the IP address of the jump server, target_server_ip_address with the IP address of the target server, and username with your username.

3. Save the file and exit the text editor.

4. To SSH to the target server via the jump server, type the following command:

ssh target_server_alias

This will automatically connect you to the target server via the jump server.

Conclusion

SSH via jump server or bastion host is essential for securing remote access to servers. In this article, we have explained what jump servers and bastion hosts are, and how to SSH via jump server or bastion host. We have also covered how to use the SSH configuration file to simplify the SSH connection process. By following the steps outlined in this article, you can securely access your servers from anywhere, anytime.

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