Catalyst 2970 which we use for installing/ghosting pc's. Now if a pc reboots during the installation process all ports are going: changed state to down. Few secs later state to up again.
Anybody some idea? It has no impact which pc is rebooting, it's with all pc's connected.
Solved! Go to Solution.
How does that work then? I've never seen that behavior: one PC rebooting causing all the ports to reset.
Are you tracking my posts to keep me honest :)
I know that turning on spanning-tree portfast will stop the port generating a TCN. I also know that a TCN does not necessarily generate a STP recalculation, it just ages out the cam tables more quickly.
But from experience i have seen this happen before with other switches. And so the solution came from experience rather than theory.
If you have an explanation i would very much appreciate it.
Don't worry Jon, I just thought I might be able to learn something new. And I have, in fact. ;-)
From time to time there are strange quirky behaviors that we can only put down "that's just the way it is", and that can only be remedied by experience. What I like about NetPro is that brainstorming with fellow networkers is much more likely to find the answer than looking for it on my own.
Perhaps the PC was generating BPDUs or something - but then not all of them could have been root ... Or perhaps it was something to do with dynamic VLAN assignment ... Or ...
I suppose an interesting thought experiment would be this: if you set some of the ports in portfast, and some without, and then you reboot a PC on a "portslow" port so that it generates a TCN, is it only the "portslow" ports that go orange, or is it all of them? That is, is it the portfast config of the switchport with the rebooting PC that makes the difference, or is it the portfast state of the other ports that determine whether they go orange or not.
If that makes sense.
No wasn't worried, just made in jest.
That's pretty much why i do NetPro as well, to keep up to date and to learn from others. Only yesterday i learnt from you that non-cisco switches will pass CDP updates from attached Cisco devices.
This problem is now going to bother me until i have a look so when i get a moment i'll see if i can replicate it in a lab and do some more troubleshooting. Big if tho !
You could have leaned the issue about CDP on non-cisco switches from me as well. Just this week there was an issue with supposed duplex mismatches that was due to this.
Make sure that you have a 3Com to test it; they all show this behaviour. Many (newer) HP switches do support CDP and treat it in the same way as Cisco boxes.
So this is one of rare occaisions where I know who is rating my posts! ;-)
Thank you. In that regard, you are a shining example for many!