I have modified the /etc/ssh/sshd_config file on the server to enable Protocol 1, just as I have in the past for earlier versions of LINUX, but ZTERM will not connect. It just times out. I can connect using an ssh client using either the -1 or -2 options.

Does anybody know of something different re SSH 1.5 protocol on CENTOS 7. ZTERM doesn't understand 2.0.

How did you activate Protocol 1? I tried it on my CentOS 7 machine by changing the default sshd_config to contain:

and restarting the service. But even then, I can't connect to it from the localhost with:

# ssh -1 -v localhost

(it says explicitly that the remote protocol version is 2.0 and therefore doesn't match the requested 1.)

The comment about explicit activation suggests maybe something additional is needed, but I can't find any further details about it anywhere. (Of course it doesn't help that virtually every Internet or other information resource relating to SSH configuration tells you to make sure to disable protocol 1, so it isn't that surprising that they are making it harder to enable, and no one has the motivation to explain how to do it.)

Perhaps it's time to switch to ATE?

Maybe on ATE, but not really my decision. Currently almost all use is from inside the network, and most connections are telnet. I'm just hoping to move to ssh as the default connection type.

Allowing protocol 1 on CENTOS 7 seems to work with no problem (ssh -1 works), but ZTERM doesn't like it. Reason: unknown-no useful error message.

Perhaps this will force a change to ATE, but was hoping to avoid the hassle of that change.

Unfortunately, I don't see how to resolve this. My guess is that they've thrown some wrench into the protocol 1 support on the server side in an effort to reduce vulnerabilities without breaking too many ssh 1 clients.

Shall I infer from this that to your knowledge nobody has connected to a CENTOS 7 server using ZTERM and the ssh protocol?

Definitely not to my knowledge. It's hard to say how many others might have seen this post, but I'm pretty sure if that if someone had tried it successfully, they would have spoken up by now.