Question : Problem: Cisco 802.1q  trunking problem

In our network we have two 4510's upstairs and one 4510 downstairs.  I am trying to run a 802.1q trunk link from one of the 4510's upstairs to a 2950 on my desk so I can access all the VLAN's.  The trunk link has come up OK, but when I assign a VLAN to one of the ports on the 2950, and add a device I start seeing other network devices getting disconnected.  I tried it in the middle of the day yesterday, and half the floor lost the file server and Exchange!  Does anyone have any ideas?

Answer : Problem: Cisco 802.1q  trunking problem

I'll sugest, posting the 2950 config as well..

Allowing all the VLAN on the trunk seem good, because you plan more vlans in the future

switchport trunk allowed vlan all

this on the 4500 and on the 2950