Which command do you enter to allow a new VLAN across a trunk?

4 thoughts on “Which command do you enter to allow a new VLAN across a trunk?”

1. C is the correct answer. It”s mentioned in the question to allow a new vlan across the trunk, it implies to add a new vlan to existing list. So it’s safe to use the term add in the command.

   reference :
   Hey if you don’t use add and set just switch port trunk allowed vlan 600 it will wipe the other vlans on the interface, that is the recommended way to add it and use remove to remove it

   It should not cause an stp change and if it did before you may have hit a bug , adding a vlan to an allowed list should not invoke any tcn notification to indicate a change.The vlan already exists in the databases all your telling it is its allowed move across the trunk , only if the trunk failed should a tcn be sent to indicate an actual topology change at layer 2

   The first way is ok and works but it can lead to human error so the add statement was introduced to make it easier to add a vlan , I have seen trunks on some nexus devices with over a 100 manual vlans allowed, in locked down networks its when your trying to copy all that in and add the vlan to problems occur as people tend to make mistakes and can end u[p actually forcing an stp change
   https://community.cisco.com/t5/other-network-architecture/quot-switchport-trunk-allowed-vlan-quot-behavior/td-p/2845616

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2. I feel like both C and D work the same way. I just tested it in packet tracer and it seems to take both commands and do the same thing. However if you type “switchport trunk allowed vlan ?” at the interface level it presents you with the option to type “add” and does not clearly indicate that you can achieve the same thing by just typing the VLAN number.

   So I think for that reason the safe answer is C

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3. No, you are adding an additional vlan so c is correct

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4. Should not be D ?

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