I have an HP ProCurve swicth configured as follows (simplified, with U for Untagged and T for Tagged):


U 1,3,5,7-10,12-16
T 2,4,6
No U 11


T 1,3,5


T 1,3,5

What is the purpose of a vlan containing only tagged ports?

What is the purpose of 2 identical vlan like VLAN_2 and VLAN_3?

1 Answer 1


What is the purpose of a vlan containing only tagged ports?

Likely, those (trunk) ports interconnect VLANs spanning multiple switches. It's also possible that a trunk leads to a VLAN-aware host or a router.

What is the purpose of 2 identichal vlan like VLAN_2 and VLAN_3?

VLANs separate layer-2 traffic. VLANs can look similar but may be used for entirely different purposes. Generally, VLAN should be properly named to document that.

  • Ah.. didn't think about vlan aware things.. and yes, multi-switch vlans.. thanks
    – user815129
    Feb 10, 2022 at 7:59
  • The most general use case of vlans is quite simple. Affect ports to different vlans and designate as trunks those used to interconnect switches and/or vlan-aware hosts. But some switch vendors complicate things (probably for more flexibility) the configuration task by introducing notions like ingress vlan egress vlan, tagged/untagged port ...etc. All these can confuse even a skilled network admin Feb 11, 2022 at 6:45
  • @SoulimaneMammar Mostly true, but tagging is generally required for trunk ports.
    – Zac67
    Feb 11, 2022 at 7:16
  • @Zac67 I know but it's more simpler to configure a port as trunk by a single command and then eventually forbid/allow some vlans on it (if there is a need) than a bunch of commands that are error prone. Network admin's life is already complicated, no need to add on that Feb 11, 2022 at 10:38
  • Yes, switchport mode trunk is easy, but Procurves/HPE Provision/Aruba don't do it that way. They require explicit tagged/untagged configuration (which I actually find more transparent) or GVRP/MVRP.
    – Zac67
    Feb 11, 2022 at 10:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.