Index: b/clientloop.c =================================================================== --- a/clientloop.c +++ b/clientloop.c @@ -502,16 +502,21 @@ static void server_alive_check(void) { - if (packet_inc_alive_timeouts() > options.server_alive_count_max) { - logit("Timeout, server not responding."); - cleanup_exit(255); + if (compat20) { + if (packet_inc_alive_timeouts() > options.server_alive_count_max) { + logit("Timeout, server not responding."); + cleanup_exit(255); + } + packet_start(SSH2_MSG_GLOBAL_REQUEST); + packet_put_cstring("keepalive@openssh.com"); + packet_put_char(1); /* boolean: want reply */ + packet_send(); + /* Insert an empty placeholder to maintain ordering */ + client_register_global_confirm(NULL, NULL); + } else { + packet_send_ignore(0); + packet_send(); } - packet_start(SSH2_MSG_GLOBAL_REQUEST); - packet_put_cstring("keepalive@openssh.com"); - packet_put_char(1); /* boolean: want reply */ - packet_send(); - /* Insert an empty placeholder to maintain ordering */ - client_register_global_confirm(NULL, NULL); } /* @@ -572,7 +577,7 @@ * event pending. */ - if (options.server_alive_interval == 0 || !compat20) + if (options.server_alive_interval == 0) tvp = NULL; else { tv.tv_sec = options.server_alive_interval; Index: b/ssh_config.5 =================================================================== --- a/ssh_config.5 +++ b/ssh_config.5 @@ -935,7 +935,10 @@ .Cm ServerAliveCountMax is left at the default, if the server becomes unresponsive, ssh will disconnect after approximately 45 seconds. -This option applies to protocol version 2 only. +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. .It Cm ServerAliveInterval Sets a timeout interval in seconds after which if no data has been received from the server,