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How To Fix “ssh_exchange_identification: read: Connection reset by peer” Error

Ubuntu 11

When working with SSH (Secure Shell) connections, you may occasionally encounter the error message “ssh_exchange_identification: read: Connection reset by peer”. This error can be quite frustrating, as it prevents you from establishing an SSH connection to a remote server. This article will guide you through several methods to troubleshoot and resolve this issue.

Quick Answer

The "ssh_exchange_identification: read: Connection reset by peer" error typically occurs when the SSH client fails to authenticate with the server, resulting in the server resetting the connection. To fix this error, you can try rebooting the server, whitelisting your IP address, restarting the sshd daemon, checking the SSH server status, reviewing firewall settings, checking SSH key authentication, and ensuring compatibility of SSH encryption modes. If none of these solutions work, it is recommended to seek further assistance from a system administrator or the server’s support team.

Understanding the Error

Before we dive into the solutions, it’s important to understand what this error message means. The “ssh_exchange_identification: read: Connection reset by peer” error typically occurs when the SSH client fails to authenticate with the server, resulting in the server resetting the connection. This can be caused by a variety of reasons, such as server-side issues, network problems, or incorrect client-side configurations.

Solution 1: Reboot the Server

The first and simplest solution to try is to reboot the server. Sometimes, a quick reboot can clear out any temporary glitches or issues that might be causing the error.

sudo reboot

The sudo command allows you to run commands with the security privileges of the superuser, while reboot is the command to restart the system.

Solution 2: Whitelist Your IP Address

The error may occur if your IP address is blacklisted by the server. To resolve this, you can whitelist your IP address. This involves checking the /etc/hosts.deny and /etc/hosts.allow files on the server.

sudo nano /etc/hosts.deny
sudo nano /etc/hosts.allow

The nano command opens a text editor in the terminal, allowing you to view and edit these files. If your IP address is listed in the /etc/hosts.deny file, remove it or add it to the /etc/hosts.allow file.

Solution 3: Restart the sshd Daemon

Another possible solution is to restart the sshd daemon on the server. The sshd daemon is the background service that listens for and manages SSH connections.

sudo systemctl restart sshd
sudo systemctl status sshd

The systemctl command is used to control systemd, the system and service manager for Linux. The restart command restarts a service, while status checks the status of a service.

Solution 4: Check SSH Server Status

Ensure that the sshd daemon is installed and running on the server. You can check the status of the sshd service using the following command:

sudo systemctl status ssh

If the service is not active, you may need to install and start the openssh-server:

sudo apt update
sudo apt install openssh-server

The apt command is used to handle packages in Ubuntu and other Debian-based distributions. update updates the package lists, while install installs a package.

Solution 5: Check Firewall Settings

Make sure that the SSH port (usually port 22) is allowed by the firewall. You can allow SSH connections by using the following commands:

sudo ufw allow ssh
sudo ufw allow 22

The ufw command is used to manage the firewall. The allow command adds a rule to allow connections on a certain port or service.

Solution 6: Check SSH Key Authentication

If you have multiple SSH keys on your client, it could exceed the value of MaxAuthTries on the server. Try increasing the value of MaxAuthTries in the sshd configuration file and restart the sshd daemon.

sudo nano /etc/ssh/sshd_config

Find the line that says MaxAuthTries and increase its value. If it’s not there, you can add it.

Solution 7: Check Compatibility of SSH Encryption Modes

Ensure that the software you are using on your computer is compatible with the SSH encryption modes supported by the server. Some software may not support certain encryption algorithms, causing the connection to be reset. Try using a different SSH client or updating your current client to the latest version.

If none of the above solutions work, it is recommended to seek further assistance from a system administrator or the support team of the server you are trying to connect to. Remember, troubleshooting is a process of elimination, and patience is key. Good luck!

For more detailed information on SSH and its related commands, you can visit the OpenSSH Documentation.

What is SSH?

SSH (Secure Shell) is a cryptographic network protocol that allows secure remote login and file transfer between computers. It provides a secure channel over an unsecured network, such as the internet, by encrypting the data that is transmitted between the client and the server.

How do I establish an SSH connection to a remote server?

To establish an SSH connection to a remote server, you need to have an SSH client installed on your local computer. You can then use the following command in the terminal:

ssh username@server_ip_address

Replace "username" with your username on the remote server and "server_ip_address" with the IP address or domain name of the server you want to connect to.

What is the purpose of whitelisting my IP address?

Whitelisting your IP address means allowing your specific IP address to connect to a server while blocking all other IP addresses. It is a security measure used to restrict access to the server and prevent unauthorized connections. By whitelisting your IP address, you ensure that only your computer can establish an SSH connection to the server.

How can I check if the SSH server is running on my server?

You can check if the SSH server is running on your server by using the following command:

sudo systemctl status sshd

If the SSH server is running, you will see the status as "active". If it is not running, you may need to start or restart the SSH server using the appropriate command for your Linux distribution.

Can I use a different port for SSH connections?

Yes, you can use a different port for SSH connections instead of the default port 22. However, you need to make sure that the SSH server is configured to listen on the desired port, and the firewall allows incoming connections on that port. To specify a different port when connecting, use the -p option followed by the port number:

ssh -p port_number username@server_ip_address

Replace "port_number" with the desired port number and "username" and "server_ip_address" as appropriate.

How can I generate an SSH key pair for authentication?

To generate an SSH key pair, you can use the ssh-keygen command on your local computer. Open the terminal and run the following command:

ssh-keygen -t rsa

This will generate a new RSA key pair. You can specify a different key type by changing the -t option. Follow the prompts to choose a location to save the key pair and set a passphrase if desired. The public key (id_rsa.pub) can then be added to the server’s ~/.ssh/authorized_keys file for authentication.

How can I change the SSH port on the server?

To change the SSH port on the server, you need to modify the SSH server configuration file. Open the file using a text editor:

sudo nano /etc/ssh/sshd_config

Find the line that specifies the port number (usually Port 22) and change it to the desired port number. Save the file and restart the SSH server for the changes to take effect:

sudo systemctl restart sshd

Make sure to update your SSH client configuration to use the new port when connecting.

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