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I have cisco switch 3560 and want to create vlans where in i can have a single port in multiple vlans. I tried creating one port e.g fa0/23 as trunk and then allowed it through multiple vlans but it doesnt work. The said port fa0/23 is not traceable through vlans.

**Example of what i am looking to establish.
Vlan 1  : fa0/1 , fa0/2 , fa0/23
vlan 2 : fa0/3, fa0/4,fa0/23
vlan 3 : fa0/5,fa0/6,fa0/23**

The Switchport multi command is not working on this switch which i always execute on cisco catalys 3500xl

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Probably you already know this, but I'm pointing it out anyway.

As Radius said, you can configure a single port in trunk mode; but this means tagged 802.1q Ethernet frames will be sent to that port, so you will need to connect to it something which can succesfully decode and detag them (like a trunk port on another switch, or a trunk port on a ESX host).

You will not be able to simply connect a computer's NIC to that port and have it connect succesfully to any one of those three VLANs. That would require 802.1q support on the computer itself.

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802.1q support is available on most linuxes, (and some windows systems, apparently). I use it regularly on my laptop to connect to a half dozen different VLANs – Tom O'Connor Jun 18 '10 at 11:10
@Tom, that's exactly what I said ("That would require 802.1q support on the computer itself."); but you wouldn't be able to simply connect an Ethernet adapter to such a port and assign an IP address to it, without quite some additional configuration. – Massimo Jun 18 '10 at 11:30

This should work if the 3 vlans are active on the switch (sh vlan to see that):

Interface fa0/3
switchport mode trunk
switchport trunk allowed vlan 1,2,3
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