TELNET hangs after firmware update to 15.3.4.6 or 16.1.3.6

[Bobby_Johnson]

We have experienced some errors that are preventing us from a full firmware update to several devices. The primary error occurs when attempting to make a TELENT connection. We are able to enter username and password, but then the session immediately hangs:
no display, no cursor, no keyboard responses.

The error occurs on multiple platforms while migrating from various versions of firmware to either v15.3.4.6 or v16.1.3.6. Here are a sampling of some of the affected devices:

Equip Model Current F/W New F/W
x650-24x 12.3.3.6 15.3.4.6
x650-24x 12.3.4.12 15.3.4.6
x460-48t 15.7.1.4 16.1.3.6
x460-24x 12.5.4.5 16.1.3.6
x450-48t 12.5.4.5 15.3.4.6
x450-48t 12.0.3.16 15.3.4.6
x350-48t 12.0.3.16 15.3.4.6

We're not sure if there is a problem with the XOS, setting, etc. The TELNET session hang DOES NOT OCCUR on all devices. We have successfully updated approx 75 already, but had to stop the update process once this error was discovered.

We have approximately 80 more devices to update, to which afterwards, they’ll have the SSH xmod installed. We appreciate any help or input you can offer.

Thanks,

Bobby

[Bobby_Johnson]

I forgot to provide feedback: Yes, the intermediate step was the solution. Even though we were at 15.3.4.6, I update to 12.5.1.6, rebooted, the updated to 15.2.4.6, rebooted and everything worked fine. Thanks for your help.

[Tripathy__Priya]

No issues. You are always welcome. Please test them with some of your old spare devices and return to us with the possible feedback later with the result.

[Bobby_Johnson]

Well, that would probably be the problem. In our previous update group, we didn't encounter such old firmware and the problem went undetected. I will coordinate with one of our less used devices and try the step process, then provide feedback.
Thanks for your help.

[Tripathy__Priya]

Would like to add one more point here which i missed in my previous post. Apart from these 12.3 or lower release others can be directly upgraded though. But as you are saying few of them experiencing telnet error hence please make sure when upgrading x460 always get the ssh mod before you upgrade and enable telnet (if disabled) before the reboot.

If you need SSH, this article will help:

https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-obtain-and-install-ssh-module/