When telneting into a CSS to troubleshoot there can only be a maximum of
4 telnet sessions. If either you or the customer does not properly
terminate your sessions they will remain active on the switch for a very
long time, unless an idle/terminal timeout parameter is configured. If
your connection is the 4th and it hangs you could be locked out
requiring a reboot unless the customer has console access. If so, they
can disconnect the connections by running "show lines", then "disconnect
vty(x)". It is a good idea to run a "show lines" to see how many
sessions there are when starting to troubleshoot. If you are not near
the limit or the customer is able to console in, no worries. If not you
may want to consider having the customer or yourself add the global idle
timeout parameter or terminal idle timer to close unwanted or idle
connections if they have not already done so. A "show run global" will
show if the idle timeout is set and "show profile" will show if the
terminal idle is configured. More information refer config guide -> configuring user profiles and CSS parameters. This
scenario is not common, but worthwhile to know!