In Linux, TCP timeout settings determine how long a TCP connection or operation should wait before assuming that a packet has been lost or a connection has become unresponsive. ![]() TCP timeout refers to the duration that a TCP connection or a network operation waits for a response before considering the process failed. The short answer is that it all comes down to TCP timeouts. But before we move forward, let’s answer an important question. So, say goodbye to frustration and hello to efficient, uninterrupted SSH sessions. This comprehensive guide unveils the secrets to maintaining active and responsive SSH connections, ensuring a seamless experience devoid of freezing troubles. Moreover, the sudden disruption of a session can lead to lost work, delayed projects, and a sense of helplessness.īut fear not, for there is a solution at hand. However, its convenience and security can sometimes be marred by a common frustration: frozen SSH sessions. ProtocolKeepAlives and SetupTimeOut are Debian-specific compatibility aliases for this option.In remote server management and secure data transfer, SSH (Secure Shell) stands as an indispensable tool. This option applies to protocol version 2 only. The default is 0, indicating that these messages will not be sent to the server, or 300 if the BatchMode option is set. ![]() Sets a timeout interval in seconds after which if no data has been received from the server, ssh(1) will send a message through the encrypted channel to request a response from the server. This option applies to protocol version 2 only in protocol version 1 there is no mechanism to request a response from the server to the server alive messages, so disconnection is the responsibility of the TCP stack. If, for example, ServerAliveInterval (see below) is set to 15 and ServerAliveCountMax is left at the default, if the server becomes unresponsive, ssh will disconnect after approximately 45 seconds. The server alive mechanism is valuable when the client or server depend on knowing when a connection has become inactive. The TCP keepalive option enabled by TCPKeepAlive is spoofable. The server alive messages are sent through the encrypted channel and therefore will not be spoofable. It is important to note that the use of server alive messages is very different from TCPKeepAlive (below). If this threshold is reached while server alive messages are being sent, ssh will disconnect from the server, terminating the session. ![]() Sets the number of server alive messages (see below) which may be sent without ssh(1) receiving any messages back from the server. ![]() These settings will make the SSH client or server send a null packet to the other side every 300 seconds (5 minutes), and give up if it doesn’t receive any response after 2 tries, at which point the connection is likely to have been discarded anyway. You can also make your OpenSSH server keep alive all connections with clients by adding the following to /etc/ssh/sshd_config: ClientAliveInterval 300 ~/.ssh/config(create the file if it doesn’t exist). To enable the keep alive system-wide (root access required), edit /etc/ssh/ssh_config to set the settings for just your user, edit In your session properties, go to Connection and under Sending of null packets to keep session active, set Seconds between keepalives (0 to turn off) To avoid having your SSH sessions become unresponsive after e.g. Sometimes the interval between session drops is 24 hours, but on many commodity firewalls, connections are killed after as little as 300 seconds. Many NAT firewalls time out idle sessions after a certain period of time to keep their trunks clean.
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