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HP4000M Vlan Configurations

Ben Taverner
Occasional Visitor

HP4000M Vlan Configurations

If i want to run 3 vlans across 0ne port what should settings should i use in respect of which vlans should be taged / untaged for that port.
3 REPLIES
Markku Leinio
Valued Contributor

Re: HP4000M Vlan Configurations

In another thread I wrote some time ago:
(note that I don't quite know the command syntax for 4000M, but the concept should be clear)

Probably Levi meant something like "how to establish a trunk connection between the switches" (just guessing).

Example: You have three VLANs in your switches: VLANs 3, 4 and 5. Both switches have several untagged ports in each VLAN. The connection between the switches can be established f.ex. like this:

vlan 3
tagged a1 (a1 is the port interconnecting the switches)
untagged b1-b8 (having the workstations)
vlan 4
tagged a1
untagged b9-b16
vlan 5
tagged a1
untagged b17-b24

When this configuration is applied to both switches, you can connect both A1s together, and then connect your VLAN 3, 4 and 5 workstations to the appropriate ports. All the three VLANs are able to traverse the A1 port and the fiber to the other switch.

The bottom line: to transfer several VLANs in one cable you have to "tag" the VLANs in the interconnecting port (one VLAN can still be untagged if desired; make consistent configurations in both ends).
Dmitry G. Spitsyn
Trusted Contributor

Re: HP4000M Vlan Configurations

It is like a trunk in Cisco devices if you use dot1q encapsulation to tag frames in VLANs.

Here any port can be an untagged member in one VLAN only. In other VLANs the port should be a tagged member. It means that in one VLAN frames will not carry any tag and will be tagged with different VLAN IDs in other VLANs.

BR,
Dmitry
OLARU Dan
Trusted Contributor

Re: HP4000M Vlan Configurations

You can leave the port "Untagged" in one VLAN, but it has to be "Tagged" for the other 2 VLANs.

Make sure you do the SAME configuration (defining VLANs, 802.1Q VLAN ID, and port tagging setting) on the other SWT, for the up-link port. You can not have a port "Untagged" for 2 or more VLANs.

The frames coming from different VLANs will be tagged by the transmitting SWT before putting them on a common up-link. The receiving SWT will look at the frame's tag (which is the VLAN's 802.1Q ID) and will forward the frame in the correct VLAN. That is why VLAN named "Engineering" must have the SAME 802.1Q ID in all the SWTs from your network.