We bough a Cisco 5500 13-slot switch to connect to our current network existing of a couple of 2950 switches with +/- 10 VLANs. Some of the ports are trunked. When I plugged in the Cisco 5500 all status led ports except the trunk ports on the 2950 switches became orange. This caused network outage.
It turned out the VLANs on the Cisco 2950 switches were removed. The ports where still assigned to a VLAN, but the VLAN did not exist on the switch.
I was wondering if anyone knows what protocol was the cause for this problem and how to disable it. I cannot just try anything, because this is a live setup and we dont have a network lab.