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VLANS across multiple switches

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Matthew Swenson
Occasional Contributor

VLANS across multiple switches

We are looking to segment our network into two groups. Most of our switches are HP ProCurve 2524 switches that go back to one main HP Switch 8000. We are looking to use VLANS on the switch 8000 to do most of the segmentation, as for most of the network all the lines that plug into the smaller switch belong to the same group. But there is one switch that will have users from both network segments. This switch will connect via fiber optic back to the Switch 8000.

What's the best way to make this connection? My initial thought is to setup two VLANS on the smaller switch. On one VLAN I'll tag all the appropriate ports and on the other VLAN I'll untag the appropriate ports. On the fiber optic link I'll have it be tagged for the one VLAN and untagged for the second. On the Switch 8000 I'll have the fiber optic link tagged and untagged to match the smaller switch.

Also, will I have to implement other VLANS on other switches in order to have the users on this split switch communicate with servers and users on other parts of the network?

Thanks for your help.

Ron Kinner
Honored Contributor

Re: VLANS across multiple switches

First on your small switch you do not tag the ports going to the hosts regardless of the VLAN they belong to. No point in it and if you do it won't work unless you setup up the host to know which VLAN its in.

On the fiber between switches you can leave VLAN 1 untagged and tag the other VLAN. (I assume you are using 802.1q). If you do not have VLAN1 then tag both of them on each end of the link.

The other switches which have only members of a single VLAN do not need any tagging. You just assign their port on the 8000 to the correct VLAN (and don't tag the 8000 port either).


Mark Landin
Valued Contributor

Re: VLANS across multiple switches

The only time you need to tag a VLAN is if a single physical port needs to belong to multiple VLANs at the same time. If that's the case, then the port needs to be tagged on all, or all but one, of the VLANS, and the other ports in the VLAN need to be set the same way.