Comment 38 for bug 1254085

Update to my comment above (#37):

I was able to connect to Box2 from OS X 10.11. I tried once more by mistake and was shocked that it suddenly worked (albeit with a long connection lag). With more testing I found I could connect from 10.11 to Box2 maybe 1/25 times (as I said, crazy making). I wasn't ever able to get to Box2 from Box1 despite trying numerous times. Long story short it looks like the Ubuntu SSH client is the most particular vs least able to win the race, followed by that in 10.11, followed by 10.9 which always connected without a problem. Interestingly when I switched to keys 10.11 was much more likely to connect (1/5 times). The switch to keys had no effect on Box1's inability to connect to Box2. So as with #36 I'd say Ubuntu's ssh client gave the worst experience here - vs - is actually the best but just needs an error message explaining why it's electing to protect me from (...?) vs "working" as my other clients did.

For those curious about the sshd aspect of the story I did finally track down a fix for Box2. Box1 and Box2 are both dual nic systems. They were configured with eth0 as static and eth1 dhcp. Plugging eth1 and letting it obtained a dhcp lease / taking that interface out of the config fixed Box2. Having the interface configured but the jack unplug produced the client dependent connection issues I outlined in #37. Box1 had the exact same interface config (eth1 looking for a dhcp lease but not being plugged in) without any problem. They are both full Intel systems but totally different hardware. Seems like the kernel abstraction leaking hardware details up the stack but understandable given both were arguably misconfigured. Imagine how annoying it would be in a dual nic system to have a port go out and suddenly arbitrarily be unable to connect to sshd with anything other than an old copy of OS X.

TL;DR - my 16.10 ssh client didn't work when others did and failed silently. This may be Ubuntu being smart. It may be Ubuntu being broken. Either repair or an informative error would make the experience better than / comparable to others.