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June 19th, 2018 21:00

SSH timeout on PowerConnect 5548

Starting with firmware version 4.1.0.21 and continuing to the newest version released this week, v4.1.0.22, I am logged out of the SSH session to my PowerConnect 5548 after one hour of inactivity.

% ssh switch; date

 
  
switch# 
  show bootvar
Unit  Image  Filename   Version    Date                    Status
----  -----  ---------  ---------  ---------------------   -----------
1     1      image-1    4.1.0.21   06-Dec-2017  16:17:06   Not active
1     2      image-2    4.1.0.22   17-May-2018  19:17:44   Active* 

"*" designates that the image was selected for the next boot

switch# 
  show version

       Unit             SW version         Boot version         HW version      
------------------- ------------------- ------------------- ------------------- 
         1               4.1.0.22            1.0.0.14            00.00.02       

switch# 
  show line ssh
SSH configuration:

  Interactive timeout: Disabled
History: 10

switch# 
  show clock
12:14:34 EDT(UTC-4) Jun 19 2018
Time source is sntp
switch# packet_write_wait: Connection to 192.168.2.X: Broken pipe
Tue Jun 19 13:14:35 EDT 2018   # date/time printed by the shell after ssh ends
 

Notice that an hour after I typed the show clock command, I am disconnected. Is there a configuration change I can make so I stay logged in, or is this a bug? If it's a bug, how can I get a bug report submitted so it can be addressed in the next release?

5 Practitioner

 • 

274.2K Posts

July 19th, 2018 12:00

I had good luck with simply setting the terminal software to send keepalive every 30 seconds.

 

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212 Posts

June 20th, 2018 09:00

Hi Joel,

You should be able to use the following for SSH, telnet, and console: 

     console(config)# line console

     console(config-line)# exec-timeout 0

Specify either the number of minutes (up to 65535, equivalent to 45 days), or use zero (0) for no timeout.

It seems counter-intuitive, but using the "no" command below will timeout with the default timing.

     console(config-line)# no exec-timeout

If the "zero" command doesn't work, try setting it to the maximum minutes or anything beyond a couple of hours and see if that also times out too soon.

Hope this helps.

June 21st, 2018 19:00

The console line was set to 10 minutes for the timeout, but I changed it just in case. It didn't work. I still got logged out one hour later.
switch# show line
Console configuration:
Interactive timeout:  10 minute(s)
History:  10
Baudrate:  9600
Databits: 8 
Parity: none 
Stopbits: 1 

Telnet configuration:
Telnet is disabled.
Interactive timeout:  10 minute(s) 
History:  10

SSH configuration:
Interactive timeout:  Disabled
History:  10
switch# conf t

switch(config)# line console
switch(config-line)# exec-timeout 0
switch(config-line)# exit
switch(config)# exit
switch# show line
Console configuration:
Interactive timeout:  Disabled
History:  10
Baudrate:  9600
Databits: 8 
Parity: none 
Stopbits: 1 

Telnet configuration:
Telnet is disabled.
Interactive timeout:  10 minute(s) 
History:  10

SSH configuration:
Interactive timeout:  Disabled
History:  10
switch# show clock 
 21:31:39 EDT(UTC-4)  Jun 21 2018
Time source is sntp
switch# packet_write_wait: Connection to 192.168.2.x: Broken pipe
Thu Jun 21 22:31:40 EDT 2018
I still think this is a bug.

June 26th, 2018 17:00

I also set the exec-timeout to 65535 to see if that had any effect.

switch(config)# line ssh
switch(config-line)# exec-timeout 65535
switch(config-line)# exit
switch(config)# exit
switch# show clock
 18:32:47 EDT(UTC-4)  Jun 26 2018
Time source is sntp
switch# packet_write_wait: Connection to 192.168.2.X: Broken pipe
Tue Jun 26 19:32:48 EDT 2018

It did not have any effect; I was still logged out of the switch after 1 hour. As an experiment, I changed it to 2 minutes and I was indeed logged out after 2 minutes, but the connection was closed in a different manner. See the close statement at the bottom? It is different from the one above.

switch(config)# line ssh
switch(config-line)# exec-timeout 2
switch(config-line)# exit
switch(config)# exit
switch# show clock 
 20:26:33 EDT(UTC-4)  Jun 26 2018
Time source is sntp
switch# Connection to switch closed.
Tue Jun 26 20:28:33 EDT 2018
versus the other close message:
switch# packet_write_wait: Connection to 192.168.2.X: Broken pipe
And, just to make sure, I set my SSH session to have the KeepAlive value to "yes", but was still logged out after an hour.

June 27th, 2018 14:00

Unrelated config lines deleted.
switch(config)# line ssh
switch(config-line)# exec-timeout 59
switch# show clock
 22:50:47 EDT(UTC-4)  Jun 26 2018
Time source is sntp
switch# Connection to switch closed.
Tue Jun 26 23:49:47 EDT 2018       timed out after 59 minutes.  Expected behavior.
switch(config-line)# exec-timeout 60
switch# show clock
 23:58:58 EDT(UTC-4)  Jun 26 2018
Time source is sntp
switch# Connection to switch closed.
Wed Jun 27 00:58:59 EDT 2018       timed out after 60 minutes.  This is unexpected.
switch1(config-line)# exec-timeout 61
switch1# show clock
 13:42:12 EDT(UTC-4)  Jun 27 2018
Time source is sntp
Connection to switch1 closed.
Wed Jun 27 14:43:12 EDT 2018       timed out after 61 minutes.  This is
unexpected. Why didn't it disconnect after 60 minutes?
switch(config-line)# exec-timeout 62
switch# show clock
 14:51:50 EDT(UTC-4)  Jun 27 2018
Time source is sntp
switch# packet_write_wait: Connection to 192.168.2.X: Broken pipe
Wed Jun 27 15:51:50 EDT 2018      disconnected after 60 minutes.
Same as if exec-timeout were set to zero

5 Practitioner

 • 

274.2K Posts

June 28th, 2018 12:00

Thanks for bringing this to our attention. I found a 5500 in our lab and currently have an SSH connection to it. I will do some further testing to see if I can reproduce these results. I will chime back in with my findings.

 

July 20th, 2018 15:00

Thank you for the information. Based on your feedback I did more research and found that I did not set the KeepAlive parameter properly in my SSH config file. I changed ~/.ssh/config (Linux host) to:

Host switch
     ServerAliveInterval 60

and that worked. I am no longer logged out of the switch unless I explicitly close the connection. Thank you again for your help.

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