2960s Cross-Stack Etherchannel problem

Brunhuber Adrian · ‎08-24-2011

Hi

I have a 2960s cross-stack ethechannel design.The switch is NOT my STP root.

My problem is when i plug a new trunk port every (trunk) port becomes orange for about 30-40 seconds.No events besides up/down for the interface i plugged in is logged.

Any ideas what is happening ? I cannot provide your more info because for the moment because i cannot interfere with the switch until a scheduled downtime.Thanks.

Amit Aneja · ‎08-24-2011

LED status orange indicates that port is in err-disabled state. In your case as you mentioned, nothing of this sort happens & you just see one message for the port up/down for the port connected to the new switch. On some switches, orange light would indicate that the port is in blocking state.

Have you noticed any communication failure through those other trunk ports which become orange?

I would look at "show spanning-tree vlan X detail" & see what's changed.

Its quite probable that STP is changing when you connect that switch.

Brunhuber Adrian · ‎08-24-2011

I also suspect a STP issue,but i wasn`t able to diagnose as the The simptoms are exactly like when the port transitions from listening/learning/forwarding state,but in every day life i plug trunk ports and this isn`t hapeping in other scenarios.The ports are not entering "error dissable" just glowing orange for 30-40 seconds and then resume normal operation.

Amit Aneja · ‎08-24-2011

It has to be STP change then. How about disabling the BPDUs coming from the new switch?

I am thinking of putting a root guard or BDU guard so that it doesn't affect our existing L2 n/w.

Peter Paluch · ‎08-24-2011

Amit,

LED status orange indicates that port is in err-disabled state

Hmmm, did you mean blocked/discarding? A port in err-disabled state is shut down, and the LED is dimmed. It should be dark.

Best regards,

Peter

Amit Aneja · ‎08-24-2011

Peter,

I meant err-disabled only. What you are saying is correct for some switches, but not for all.

I have seen cases wherein LED colour would be orange when port is err disabled.

Infact there was a bug filed on this as well, where LED would turn off instead of being orange. So, this was documented as abnormal & bug was raised.

Please take a look at the notes of CSCtr13789.

Please take a look at the following doc as well:

http://www.cisco.com/en/US/customer/tech/tk389/tk621/technologies_tech_note09186a00806cd87b.shtml

If the configuration shows a port to be enabled, but software on the switch detects an error situation on the port, the software shuts down that port. In other words, the port is automatically disabled by the switch operating system software because of an error condition that is encountered on the port.

When a port is error disabled, it is effectively shut down and no traffic is sent or received on that port. The port LED is set to the color orange and, when you issue the show interfaces command, the port status shows err-disabled. Here is an example of what an error-disabled port looks like from the command-line interface (CLI) of the switch:

Regards,

Amit

Peter Paluch · ‎08-24-2011

Amit,

This is very interesting, and thanks for pointing that out to me.

It seems that this behavior is platform dependent. The document you have referenced seems to imply the LED behavior for 6500 Catalyst series. However, for several years, I routinely work with 2950/2960/3560, I have seen lots of err-disabled ports and I am absolutely sure that an err-disabled port on these platforms had the LED always turned off. This also aligns with the fact that an err-disabled port on these platforms behaves essentially like a deactivated port, including a link-down status (attached devices report no connection on the physical layer).

Best regards,

Peter

Amit Aneja · ‎08-24-2011

Peter,

I agree with you & this is strange. I have seen this before in my lab on one of the 3k switches, that's when I came to know about this behavior. It was approx 3 years ago. Infact, the bug ID that I mentioned is filed for 3560 switch & it clearly says the LED should go orange rather than getting turned off.

I will see if I can research & post the exact LED status for most of the 3k, 4k & 6k switches.

Regrads,

Amit

Fabio Francisco · ‎08-24-2011

What version of STP are you running?

Brunhuber Adrian · ‎08-24-2011

RSTP.

I think i have found the issue.I wasn`t been able to test it but recently the client plugged an old router with a HWIC.The hwic had a lower bridge ID so it became the root of STP.I will reconfigure today the entire STP domain with rootguard and the corect STP root and let you know.

Thanks everybody.