All Errors

This error occurs when the SSH client and server cannot agree on a Message Authentication Code (MAC) algorithm during the connection negotiation phase. It happens when newer SSH clients attempt to connect to older servers, or when security policies have disabled certain algorithms.

The SSH daemon (sshd) fails to start with "fatal: Cannot bind any address" when it cannot listen on the configured address or port. Common causes include address family mismatches, ports already in use, network startup timing issues, and SELinux permission restrictions. Most solutions involve fixing sshd configuration or checking service startup order.

This error appears when SSH detects that a host's key has changed since you last connected. It's a critical security check that prevents man-in-the-middle attacks, but is often triggered legitimately when servers are reinstalled, IP addresses are reassigned, or infrastructure is recreated.

The ssh-keygen command prompts for confirmation when an SSH key file already exists at the target location. You need to decide whether to overwrite the existing key, use a different filename, or keep the existing key.

This error occurs when the SSH client tries too many authentication methods before the server's maximum attempt limit is reached. The server disconnects to prevent brute force attacks. Usually caused by offering too many SSH keys or having multiple identity files configured.

The SSH key exchange process is interrupted when the remote server closes the connection before authentication can complete. This typically indicates network issues, firewall blocking, server overload, or security restrictions.

This error occurs when the SSH server abruptly terminates the connection during the key exchange phase, before authentication completes. It's typically caused by firewall blocking, network issues, server misconfiguration, or resource exhaustion.

The 'Network is unreachable' SSH error occurs when the client machine cannot establish a network route to the remote host. This typically results from missing network connectivity, incorrect routing configuration, firewall blocking, or the remote host being offline. Unlike connection refused errors, this indicates the network path itself is unavailable, not that the SSH service is unreachable.

This error occurs when the SSH client detects that a server's ECDSA host key has changed from what is stored locally. It's a security warning that prevents automatic connection to the server, requiring you to verify that the host hasn't been compromised or replaced.

This error occurs when the SSH client or server encounters an invalid or misspelled configuration option. It typically indicates a typo in your SSH config file, use of a deprecated option, or an option that's not supported by your SSH version.

This error occurs when an SSH client cannot establish a TCP connection to the SSH server on the remote host. It typically indicates a network connectivity issue, incorrect hostname/port, or the SSH service isn't running or accessible.

The SSH daemon (sshd) cannot start because it cannot find or access its host keys. Host keys are cryptographic credentials that identify the SSH server to clients, and they must exist and be accessible for sshd to operate. This error typically occurs after a fresh installation, accidental deletion, or permission changes that prevent sshd from reading the keys.

This error occurs when the SSH server abruptly closes the connection during the key exchange phase, before authentication completes. Common causes include firewall blocks, IP bans, misconfigured SSH service, or network issues.

This error occurs when an SSH client (or server) exceeds the maximum number of authentication attempts. The SSH daemon disconnects the connection to prevent brute force attacks and excessive failed login attempts.

This error occurs when the SSH server (sshd) denies a channel opening request for port forwarding, tunneling, or subsystem operations. It means the server is configured to administratively prohibit the requested operation, even though the authentication succeeded.

This warning occurs when SSH stores different ECDSA keys for the same host accessed via both its hostname and IP address. It typically appears after a server reinstall, key regeneration, or when connecting via multiple identifiers. The warning is usually harmless but indicates SSH can't verify the connection is to the expected host.

The SSH client receives a connection reset error during the key exchange phase when attempting to establish an SSH connection. This typically indicates a network issue, firewall blocking, or SSH server misconfiguration.

This message appears in SSH logs when the SSH daemon (sshd) receives signal 15 (SIGTERM), a graceful termination request. It typically indicates a service restart or system shutdown, not necessarily a connection error.

SSH cannot translate the hostname to an IP address due to DNS resolution failures, incorrect hostname spelling, network connectivity issues, or misconfigured DNS settings. Fix by verifying hostname spelling, checking DNS resolution, updating /etc/hosts, or using the IP address directly.

The SSH key exchange phase fails when the remote server closes the connection before completing the identification handshake. This typically occurs due to network issues, firewall blocks, server overload, or configuration mismatches.