Hi All, I'm seeing something which I would not believe could happen had I not seen it for myself.? It's intermittent and thus not easily repeatable. On client, I ran: "ssh -i cert -x -T -oBatchMode=yes example.com batchjob" and ssh exited cleanly, immediately, and displaying no output.? When I saw it, I repeated the command, with the same results, a few times. On example.com, cert.pub is installed in .ssh/authorized_keys. Batchjob is executable and in PATH, and starts (after #! /bin/sh) with "echo "`date`: $0 $*" >> /tmp/log".? Nothing appeared /tmp/log for those occassions when client's ssh exited cleanly, immediately and without displaying output.? Nothing appeared in /var/log/syslog to indicate that something was awry. The one clue that I can think of, if it is a clue, is that I have two DNS A records published for example.com, one for the primary instance and the other for a hot-backup.? Both are virtual servers hosted on different Linux servers.? The primary is running and the hot-backup is not.? DRBD is used to keep the hot-backup synchronised with the primary.? The idea is that I can switch server roles without needing to reconfigure client.? My experience is that openssh tries all A records in sequence until it connects and that this is a viable strategy. I feel that openssh would print something if it was unable to get a connection, and, that having got a connection, example.com would print something to /tmp/log.? For ssh to cleanly exit with nothing output and nothing logged stumps me. Example.com is x64 architecture running Ubuntu 16.04.5.? It's reasonably up-to-date except for openssh-server, which is 1:7.2p2-4ubuntu2.4. Client is Raspberry Pi 3B+ running Raspbian 9.4.? Openssh-client is 1:7.4p1-10+deb9u3. Both machines have plenty of free memory. It's uncommon for me to reach out for ideas, but I'm reaching out now.? Any ideas? Thanks in advance. David