We have around 50 remotes switches which are connected via a lease line, only 3 switches are not able to telnet, while try to telnet:
The switch will stop responding to the monitoring system, ping will request timeout (before telnet to the switch, that switch can be ping all the time)
After reboot the switch can telnet without any problem and can be ping (after 15 minutes then will back to above scenario, try telnet will fail and cannot ping anymore)
While console to the switch, no error message show on the log, or high cpu or any unusual issue.
Above problem switches are running is different IOS version, like:
c2950-i6q4l2-mz.121-12c.EA1.bin
c2950-i6q4l2-mz.121-9.EA1.bin
c2950-i6q4l2-mz.121-6.EA2a.bin
Some remote switches running above IOS and same configuration, but without any issue to telnet it, only these 3 switches having the problems.
Similar to below case:
https://supportforums.cisco.com/thread/27315
