I understand how VLANs work, but am not quite sure what the various settings in my HP switch actually do.

I have an HP 1910 switch, and I'm using the web interface to configure it (personally I'd prefer the CLI, but we have some CLIphobic people involved).

I can set a port to be a tagged or untagged member of a VLAN. I can only set one untagged VLAN on a port, which makes sense. I can also set the port type to Access, Trunk or Hybrid.

What I don't understand is how those two options combine. Why would I set a port as Access, and have it a tagged member of multiple VLANs?

What is the difference between Access, Trunk and Hybrid, and how do they differ in how they handle incoming and outgoing tagged and untagged traffic?

  • I'm curious about the same. This never made sense to me either and the HP manual isn't very clear. It just states the options (duh, the web-interface is clear enough) but doesn't really explain the consequences of any given choice. – Tonny Jan 14 '14 at 22:30
  • "What I don't understand is how those two options combine. Why would I set a port as Access, and have it a tagged member of multiple VLANs?" Imagine a large office where the port goes to a punch-down or a wall plate. The port could be used by different people or by multiple vlans e.g. host to voip phone to wall jack. It's a matter of which resources do you want to manage. Sometimes you have enough bandwidth that vlan broadcast domains are immaterial, sometimes you have a lot of movement on a jack, it depends on the resources on hand. – Rookie Jan 14 '14 at 23:21

I believe I have found the answer on page 148 of the HP 1910 User Guide

For inbound untagged frames:

  • Access port will tag the frame with the PVID of the port.
  • Trunk and Hybrid will check if the PVID of the port is permitted on that port, and tag it. If the PVID is not one of the ones allowed on the port, the frame is dropped.

For inbound tagged frames:

  • Access port will pass the frame along if the VLAN tag matches the port's PVID. Otherwise it will drop the frame.
  • Trunk and Hybrid will receive the frame if the VLAN is one of the ones allowed on that port, otherwise they drop it.

For outbound traffic (this is where Trunk and Hybrid differ):

  • Access port will remove the VLAN tag, and send the frame untagged.
  • Trunk will remove the tag if it matches the PVID and the port belongs to the PVID. It will send it with a VLAN tag if the VLAN is carried on that port, but different from the PVID.
  • Hybrid will send the frame tagged or untagged, depending on whether the VLAN is set for tagged or untagged membership. Hybrid ports can have multiple untagged VLANs.

This still doesn't give a satisfactory explaination of hybrid ports, but explains everything else well enough. Hopefully someone can add some information about hybrid ports.

  • I thought hybrid ports could have one untagged and multiple tagged vlans. – toppledwagon Jan 15 '14 at 21:02
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    @toppledwagon According to the documentation, trunk ports can have one untagged and multiple tagged. Hybrid can have multiple UNtagged. Which makes absolutely no sense to me...why would you do that? Hoping someone can clear that part up. – Grant Jan 15 '14 at 21:10

Traditionally you use either of the two modes

  1. Access - Can have single untagged VLAN
  2. Trunk - Single Untagged VLAN + Multiple Tagged VLANs

The new mode is Hybrid which allows multiple untagged VLANs on the same port which was not possible in the above two modes

One use case of Hybrid mode is when you connect an IP Phone to the switch and a PC connected to IP Phone's switch port. To make two VLANs work - one data and one Voice, we have been making the Voice VLAN as tagged and Data VLAN as untagged and the switch port in trunk mode.

With the switch port in Hybrid mode, both VLANs can be untagged.

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