I want to turn on vlan tagging on my main cisco catalyst 3560 so that frames leaving the switch are tagged (and visible on my layer 2 managed switches on the far side of my network) but at the same time I also want to accept both tagged and untagged frames until I can better map the network. I do have other brands of switches that I'll be getting to work with the vlans defined on this 3650 (etherwan and 3COM/HP) so 802.1Q tagging is what I'm going with and, eventually, I need to be able to have the vlans span (?) from the primary switch to the others.

Can someone help me get started with the IOS foo to accomplish some of this? I have VLANs configured but I don't see any tagging in the frames.

  • Before we can help you, you need to identify, for each port: What VLANs are carried & Which VLAN is untagged. You can't just say "Oh, allow tagged and untagged frames." – MikeyB Jul 28 '11 at 4:51

Once you've identified your exact requirements above:

Each VLAN needs to be created before traffic will pass:

Switch(config)# vlan [number]
Switch(config-vlan)# name [name]

For each trunk (>1 vlan) port, config as follows. Let's say 1000 is native (untagged) VLAN and 2000-2100 and 3000 are carried:

Switch(config)# int gi0/1
Switch(config-interface)# switchport mode trunk
Switch(config-interface)# switchport trunk allowed vlan 1000,2000-2100,3000
Switch(config-interface)# switchport trunk native vlan 1000

For each access (1 vlan, untagged) port, config as follows:

Switch(config)# int gi0/2
Switch(config-interface)# switchport mode access
Switch(config-interface)# switchport access vlan 1000

You can also specify and interface range: Switch(config)# int range gi0/1 - 10, gi1/1

And shorten commands if the keywords are still unique: Switch(config-interface)# sw tr na vl 1000

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  • 2
    Native vlan would need to be in the allowed vlan list on g0/1, too. – Shane Madden Jul 28 '11 at 15:08
  • Right, duh… the things you forget at 2am – MikeyB Jul 28 '11 at 15:43

cisco usually by default will enable it as 802.1q but i would also add in the trunk side: switchport trunk encapsulation dot1q then state teh trunk allowed vlans

mikeyB nailed it though!

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