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Stacked 2920s and VLANS

Occasional Contributor

Stacked 2920s and VLANS

Hi All,


I think this might be a bit of a silly query but wanted some confirmation before we invest in a couple of 2920s.


We have a project to upgrade our virtualisation SAN and will be purchasing a new Nimble appliance to replace an old legacy one.  We''ll also be replacing the switches on our iSCSI network and have earmarked two 2920s in a stacked configuration.


My concern is in regards to how VLANs work in a stack.  I've taken a good look at the Advanced Traffic Management guide and the bit that has caught my eye is the statement that 'Stacking uses only the primary VLAN on each switch in a stack.'  Does this mean that the primary VLAN is only used to estabish and maintain the stack?  The way our configuration is going we would create 4 additional VLANs for 4 seperate subnets of iSCSI traffic, enabling the SAN and VM hosts to each use 4 x GbE connections with MPIO.  Normally we would mark the ports used for each iSCSI VLAN as untagged, thus dedicating those ports to each iSCSI subnet; would this configuration work with such a stack?  I'd like to think so as I wouldn't have thought that HP would launch a stacked solution where network traffic on both switches can only traverse the primary VLAN.


Like I say I might be worrying over nothing but if anyone can confirm or offer any advise in this area it'd be most appreciated.


Many thanks in advance.


Honored Contributor

Re: Stacked 2920s and VLANS

Before the 2920 and 3800 came out, HP didn't have a proprietary local stack interconnect on Procurve. However, folks asked for stacking and they came up with a scheme where switches could autodiscover each other over the LAN, and be managed from one IP address and called that stacking.


Now they have stacking, it's important not to confuse it with stacking. I wouldn't read anything in the half-assed stacking chapter (6) applying to proper stacks (chapter 7).