I have a Cisco 3560 switch and I have configured a port as a trunk port like this:
switchport mode trunk
swithport trunk encapsulation dot1q
I also have an Intel Network card PRO 1000 GT in a desktop computer and I have configured multiple VLANs on the NIC. I cannot get them to work at all. I have tried different ports on the switch, a different switch (Cisco 3750) and still no luck.
The NIC works fine if I don't setup the VLANs on it. It also works fine if I setup an "untagged VLAN". (i.e. switchport trunk native vlan 100).
I called Intel and they seem to think it's a configuration problem on the Cisco switch.
I'm thinking the frames are being tagged differently somehow and that's why it's not working.