VLAN configuration 3COM (simple question)

[SjoerdvW]

I never worked with 3COM switches, mostly the traditional Procurve switches.

I've to place a new procurve to a network with 3Com 5400 switches, and create a new VLAN.
The 3com's are configured to use the default VLAN 1.
I'm adding a VLAN (2) and want this VLAN available on both the 3COM and the Procurve.

Normaly i use the CLI but since in totaly new to 3com I use the webinterface to configure this switch.

There's something I don't understand about this 3coms: I added the new VLAN, and created a trunk to the procurve, now i untag some ports to this new VLAN. After this the port is still untagged to VLAN 1 also. Im not able to configure the port as "Not A Member" for VLAN 1. (I receive an error message "VLAN 1 can not be modified").

How is it possible to untag multiple VLANs on 1 port? (on witch VLAN are the computers attached to those ports?)
Why can't I remove the untag for VLAN 1 on those ports?

[Fred_Mancen_1 · Accepted solution]

Hi.

The VLAN 1 is the default VLAN in any switch from any vendor. If you set up a port as a trunk, it's normal that VLAN 1 remains in the port settings as untagged. If you want to remove the VLAN 1 from port, you have to open the console in the browser, go to Device > VLAN > Modify Port, then setup the desired VLAN in the port you chose as "Not a member", then apply the settings.

Using CLI you will see that the port is in the link-type hybrid. Enter the command "undo port hybrid vlan 1 untagged" in the desired ports. The hybrid mode supports many untagged VLANs and many tagged VLANs simultaneously.

Regards.

[SjoerdvW]

Thnx! In the original Procurves its not possible to untagg a port in multiple VLANs. I still dont't understan why someone whould need this.

Figured out that you can set a PVID on the port. When i set the PVID to my new VLAN ID, everythig seems to work fine (even when its still untagged in VLAN 1)

[paulgear]

I'm only new to A series, so i just read the documentation on hybrid ports.  I can't see any reason why anyone would want to use them.  The whole point of VLANs is to separate the traffic, and adding multiple VLANs to a hybrid port mixes their traffic back in together untagged.  The only plausible scenario i can see for using them (and the only way they could conceivably separate incoming traffic into the correct VLANs) is if you're using protocol-based VLANs or one of the other unusual VLAN types.  I'll be staying right away from hybrid ports.

[chrisuk85]

The main use for hybrid ports in my experience is when using VoIP. Ports are configured to enable phones and PCs to use the same port. In this scenario, I set the link type as hybrid and then set the voice vlan id as tagged. The default VLAN (which we used for PCs) is of course left untagged on this port.

In this scenario I am not quite clear as to if you were talking about switch to switch links, or ports for hosts...but if it's a host port you can remove it from VLAN1 by making it an ACCESS port in whatever VLAN you wish for it to be in.

I too however have so far struggled to see why you would want to use hybrid ports to have many VLANs untaged..

As far as I am aware that is the only difference between hybrid and trunk...

[paulgear]

Hmmm... Are you saying that there can't be any untagged ports on a trunk link?  if that's the case, i can see myself using hybrid links a lot, especially for switch-to-switch links.  I need to go back over the A Series VLAN doco.  This is one area where i think E series is much better: you just pick which VLAN you want untagged, and which VLAN you want tagged, and you don't have to care about some arbitrary notion of "mode".

[paulgear]

I reviewed the doco, and the A series trunk ports definitely allow an untagged VLAN (the default, or PVID). So using a trunk port to get to a VoIP phone + PC combo would work the same as a hybrid port.

If i understand the doco and the CLI correctly, hybrid ports are identical to trunk ports, except that they allow multiple untagged VLANs. If that's the case, i can't see any use for a hybrid port except in the case of protocol- or subnet-based VLANs.

As an A-series newcomer, i would appreciate it if any experts on the matter could clarify this.

[pombeii]

You are right. The most important difference between hybrid and trunk is that a hybrid port can be untagged in multiple VLANs but a trunk port can be untagged only in the PVID VLAN. (The PVID was previously called the default VLAN of a port, but to avoid confusion with the default VLAN, VLAN 1, it is now simply called PVID.)

Hybrid ports are not designed for switch-to-switch links, even though you can use the ports for that purpose.  They are designed for flexibility to support the emerging applications, including multicast VLANs (see IP multicast docs), some security features (such as MAC-based 802.1X, guest VLAN on ports that perform MAC-based access control, see Security docs), voice feature,  protocol-based VLANs, subnet-based VLANs.

So why we need a hybrid? because it is more flexible than access and trunk.

[paulgear]

Thanks for the clarification. I must admit i am keen to see ProVision CLI compatibility features added to the A-series. The E-series "tagged"/"untagged" is a much cleaner and simpler nomenclature.