Question : Problem: trunk Cisco 2950 to Cisco 3550

I have a cisco 2950 that (should) connect a cisco 3550
I wanted to set a trunk using: switchport trunk encapsulation dot1q (which I use anywhere else in my network)
but the 'encapsulation' doesn't work on that switch
what is the best way to configure the uplink from 3550 to 2950?
the 3550 is the main switch & connect to 3 different VLANs,
I want the 2950 to allow connection to all 3 VLANs

Answer : Problem: trunk Cisco 2950 to Cisco 3550

OK, let's start from the beginning... are you using a crossover cable? Does it work if you turn trunking off?