Does it happens only on an SSH session or does it happens also when you simply telnet into the switch? Also does it happens only when you have all five SSH sessions or can it happens when only one SSH session is active. How easily is it to reproduce? Do you have to do "show spanning" repeatedly over many times to reproduce it?
Any info that might help me reproduce the problem is appreciated.
I have tried with both SSH and regular telnet sessions. I have executed the show spanning tree operation more then 50 times on each type of sessions. I also tried with multiple telnet & SSH sessions active. I'm using SSH on cygwin and on Linux. No luck reproducing it.
Can you give me more information please. When you said it locked up on you, does it hangs only the given SSH session so that you can access it with another SSH session? If so maybe something to do with your particular SSH tool. What are you using? Is it SSH that comes with Linux or something on windows?
Does the console show any message when a session "locks up" on you? Any other observation that might help?
I think I figured out the problem. It seems that some SSH clients on windows will seem to lock up when use with the switch. It maybe that the performance on these clients are so slow that they look as if they lock up when executing commands that result in a lot of data being returned (such as "show spanning").
I have downloaded and tried a number of different SSH clients on Windows and I find that there are really three types:
Also when these slower clients are killed they do not release the session which cause the problems you notice where the sessions are locked open. In fact if you are really patience these clients do eventually response just take a VERY long time.
I suggest you use the OpenSSH based clients on windows or the SSHSecureShellClient for better performance.
Ok. Let me try this config on my switch and I will let you know. However, I have been unable to reproduce your problem on my current system using various different SSH implementation on Linux including OpenSSH. Maybe its related to your configuration. Anyway, I will load your config and try it.
Also, have you tried it with just telnet just to eliminate the SSH issue?
I've loaded a configuration very similar to yours. The difference is that I'm using VLAN1 for management and I adjusted the IP address to fit my network, and of course I changed the login password. Otherwise the configuration is very similar to what you have. I have executed the "show span" on this switch for more then 50 times using both SSHClient on windows and OpenSSH on Linux. I have not had any problem. I also tried using telnet with similar result.
When you run this, does it seems slow on any other command? Meaning that do you experience a general slowness that might be attributable to having to encrypt/decrypt using SSH? Or do you normally see everything working with good performance and experiencing a problem only on the "show span" command? Also does it "lock up" when it is "gathering information..." to display the spanning tree or in the middle of dumping the data to the screen?
Can you attach a console to the serial port of the switch while executing your command to see if there is any messages printed to the console that might help to diagnose this problem.
At this point I'm really at a lost. I cannot reproduce the problem on my network and I'm not sure what you are seeing. I can't figure out whether the problem you are experiencing is SSH related or something else. If you could reproduce it using only telnet then it might help to eliminate SSH as the possibility.
I tried duplicating the issue using a 3448 that provides link to all of our lab systems (different lab than Cuoung) and was also unable to find a problem. I issued the "show span" (using both "terminal datadump" and "no terminal datadump" 100 times and experienced no lockups. I also tried hopping through more than one SSH tunnel by using PuTTY to connect from my Win2k3 server to my RHEL4 U1 server and then SSHing into the switch, but saw no difference.
3448 fw - 18.104.22.168openssh-3.9p1-8 (RHEL4 U1)3448 uptime - 24 days
Is the problem intermittant? If you reboot the 3448 does it appear to work for an unknown amount of time? What is the uptime for one of the switches on which you've seen this problem?
Message Edited by nickw- on 10-14-2005 11:51 AM