SSH is widely used for secure logins to remote systems, but slow authentication can be a significant bottleneck. This delay becomes more problematic when you need to log in multiple times throughout the day. Optimizing SSH performance is essential to reduce these delays and enhance productivity.
Various factors can affect the speed of SSH authentication. These include reverse DNS lookups, GSSAPI authentication, and the methods used for connecting. By adjusting both server and client configurations, you can significantly improve SSH connection times, making remote access more efficient.
Implementing a few straightforward changes can lead to noticeable improvements. From disabling unnecessary authentication checks to enabling connection sharing, each step contributes to faster SSH logins. These adjustments will help streamline the process without compromising security.
Steps to improve SSH performance:
- Disable reverse DNS lookup on the SSH server.
SSH server could be configured to perform a reverse DNS lookup of incoming connection which could delay the log in process.
- Disable GSSAPI authentication on the SSH server.
SSH server might have to check if you're using GSSAPI authentication even if you're conecting via other authentication method.
- Enable multiplexing to share and reuse SSH connections.
multiplexing allows sharing and reuse of SSH connection which could significantly speed up remote SSH server access.
Related: share-connection-with-multiplexing
- Specify the authentication method manually in the SSH client.
SSH client will try multiple authentication methods unless manually specified.
- Use passwordless authentication.
Not having to manually key in username and password during log in will speed up SSH authentication.
- Use faster encryption algorithms.
Configure the SSH server and client to use faster algorithms like `chacha20-poly1305` by setting `Ciphers` in both sshd_config and ssh_config files.
Related: How to change SSH ciphers
Mohd Shakir Zakaria is a cloud architect with deep roots in software development and open-source advocacy. Certified in AWS, Red Hat, VMware, ITIL, and Linux, he specializes in designing and managing robust cloud and on-premises infrastructures.
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