Bug 2029

I have a dual IPv4/6 server which has both A and AAAA records
  published for it's primary domain name.  I had just rebooted the
  server for a kernel update and was trying to ssh back in.  It failed
  with a "network unreachable" error which was totally misleading.  The
  issue was that the server was slow to come up and was not listening on
  port 22 yet.  The error message should have been "connection refused".

  During the period when I was waiting, if I used ssh directly to the
  IPv4 address, I (correctly) got "connection refused".  When I ssh'd to
  the IPv6 address I (also correctly) got network unreachable since
  there is no IPv6 connectivity other than link-local on the network the
  ssh client was connecting from.

  it looks like what ssh is doing in the case of a host with dual A/AAAA
  records is looking them both up, trying both connections, and if the
  case of both failing, it's returning the IPv6 error message.  In this
  case it was quite confusing as there's no indication it's an IPv6
  connection the message is about.  I was trying to figure out how I
  could ping the server and at the same time have the network be
  unreachable.

  It would be better if, in the case of two errors, network unreachable
  is only handed back to the user if no other error (such as connection
  refused) does not indicate that the network was reachable and a
  connection to the remote server made at some level.