Problem with Core switch and distribution switches

[Heba Ghonamy]

Hello all,

I hope any one can help me in this issue :

we have core switch 3750 connect with 14 distribution switches 2960 with 2 uplink each , 3 switch work on speed 100 when i change one to 1000 i notice a strange behavoir in the enviroment the switch goes up and down and i cann't stop them

[Jose Solano]

Hi,

When this happens do you see any logs, errors, high cpu or any issues like that? Also what do you mean by the switch goes up and down?

[Leo Laohoo]

we have core switch 3750 connect with 14 distribution switches 2960 with 2 uplink each , 3 switch work on speed 100 when i change one to 1000 i notice a strange behavoir in the enviroment the switch goes up and down and i cann't stop them

There could be two reasons to this behaviour:

1.  Faulty cable; or

2.  Cable run > 100 metres.

From the 3750, try to run a TDR test.

[Heba Ghonamy]

Thank you Leo Solano & Leo Laohoo the problem was with STP when i shutdown the port-channel of the uplinks to the coreswitch

[Leo Laohoo]

the problem was with STP when i shutdown the port-channel of the uplinks to the coreswitch

This does not make any sense.  STP does NOT change the speed of your links.  Besides, how is your uplink configured and why does your uplink have STP enabled? 

[Heba Ghonamy]

When i change the speed of the port-channel first i shutdown the port-channel that make all the edge switches go up and down which make me restore the configuration and start again without shutting the pot-channel