I would make sure the Firmware is up to date (C.09.04). There was an issue in earlier FW where telnet sessions did not get released correctly.
Another thing to do is under SYSTEM CONFIG, set the SESSION TIMEOUT to something other than "0" (600 seconds will set it to 10 minutes) so that if there is no activity the ATLAS will terminate a telnet session.
This should clear any telnet sessions even if they are terminated incorrectly.
Hope this helps,
Thanks, I can't see the settings right now because I can't get telnet to work but the next time I reboot the units I will try your suggestions.
I have two of these Atlas 550 units with C.09.04, the Telnet stops working on both units unless I do a reboot of the device. The timeout is set to 600 seconds.
Self test results
x 1 07:09:21 06/23 S0 3 HDLC Passed x 2 07:08:59 06/23 S0 4 HDLC Passed x 3 07:08:37 06/23 S0 0 DRAM Tst Passed x 4 07:08:27 06/23 S0 0 TDM RAM Tst Passed x 5 07:08:26 06/23 S0 0 NV Batt Tst FAILED x 6 07:08:26 06/23 S0 0 RTC RAM Tst Passed x 7 07:08:26 06/23 S0 0 DSP RAM Tst Passed x 8 07:08:26 06/23 S0 0 Bootrom Tst Passed x 9 07:08:26 06/23 S0 0 Flash Tst Passed x 10 07:08:20 06/23 S0 0 Test Start
The "NV Batt Tst FAILED" indicates the NVRAM battery (chip U4) has died. You can look at this post https://supportforums.adtran.com/message/4401#4401 which discusses the NV Battery and how it will cause the unit to loose configuration on a reboot.
For the Telnet sessions that stop working, be sure to log out properly (using ctrl+l) before closing the telnet client software.